National Semiconductor DP83848C Technical data

DP83848C PHYTER® - Commercial Temperature

DP83848C PHYTER

May 2008

Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver

General Description

The DP83848C is a robust fully featured 10/100 single
port Physical Layer device offering low power con­sumption, including several intelligent power down
states. These low power modes increase overall prod­uct reliability due to decreased power dissipation. Sup­porting multiple intelligent power modes allows the
application to use the absolute minimum amount of
power needed for operation.

The DP83848C includes a 25MHz clock out. This
means that the application can be designed with a
minimum of external parts, which in turn results in the
lowest possible total cost of the solution.

The DP83848C easily interfaces to twisted pair media
via an external transformer. Both MII and RMII are
supported ensuring ease and flexibility of design.

The DP83848C features integrated sublayers to sup­port both 10BASE-T and 100BASE-TX Ethernet proto­cols, which ensures compatibility and interoperability
with all other standards based Ethernet solutions.

The DP83848C is offered in a small form factor (48 pin
LQFP) so that a minimum of board space is needed.

Applications

• High End Peripheral Devices

• Industrial Controls and Factory Automation

• General Embedded Applications

Features

• Low-power 3.3V, 0.18µm CMOS technology

• Low power consumption < 270mW Typical

• 3.3V MAC Interface

• Auto-MDIX for 10/100 Mb/s

• Energy Detection Mode

• 25 MHz clock out

• SNI Interface (configurable)

• RMII Rev. 1.2 Interface (configurable)

• MII Serial Management Interface (MDC and MDIO)

• IEEE 802.3u MII

• IEEE 802.3u Auto-Negotiation and Parallel Detection

• IEEE 802.3u ENDEC, 10BASE-T transceivers and filters

• IEEE 802.3u PCS, 100BASE-TX transceivers and filters

• Integrated ANSI X3.263 compliant TP-PMD physical sub-

layer with adaptive equalization and Baseline Wander com­pensation

• Error-free Operation up to 137 meters

• Programmable LED support Link, 10 /100 Mb/s Mode, Activ-

ity, and Collision Detect

• Single register access for complete PHY status

• 10/100 Mb/s packet BIST (Built in Self Test)

• 48-pin LQFP package (7mm) x (7mm)

®

— Commercial Temperature Single Port 10/100 Mb/s Ethernet Physical Layer Transceiver

System Diagram

10BASE-T

MPU/CPU

PHYTER® is a registered trademark of National Semiconductor.

© 2008 National Semiconductor Corporation www.national.com

MII/RMII/SNI

Media Access Controller

DP83848C

10/100 Mb/s

25 MHz
Clock

Source

Typical Application

1

Status

LEDs

Magnetics

RJ-45

or

100BASE-TX

MII/RMII/SNI

DP83848C

TX_CLK

TXD[3:0]

TX_DATA TX_CLK

10BASE-T &

100BASE-TX

Transmit
Block

SERIAL

MANAGEMENT

TX_EN

MDIO

MII/RMII/SNI INTERFACES

COL

MDC

MII

Registers

Auto-Negotiation

State Machine

CRS/CRS_DV

RX_DV

RX_ER

RX_CLK

10BASE-T &

100BASE-TX

Receive
Block

RX_CLK

RXD[3:0]

RX_DATA

DAC

Clock

Generation

Auto-MDIX

TD±

Figure 1. DP83848C Functional Block Diagram

LEDS

RD±

REFERENCE CLOCK

ADC

LED

Drivers

www.national.com 2

1.0 Pin Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

1.1 Serial Management Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

1.2 MAC Data Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9

1.3 Clock Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

1.4 LED Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

1.5 Reset and Power Down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

1.6 Strap Options . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

1.7 10 Mb/s and 100 Mb/s PMD Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

1.8 Special Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

1.9 Power Supply Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

1.10 Package Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

2.0 Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.1 Auto-Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

2.1.1 Auto-Negotiation Pin Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.1.2 Auto-Negotiation Register Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2.1.3 Auto-Negotiation Parallel Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.1.4 Auto-Negotiation Restart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.1.5 Enabling Auto-Negotiation via Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.1.6 Auto-Negotiation Complete Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

2.2 Auto-MDIX . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

2.3 PHY Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

2.3.1 MII Isolate Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

2.4 LED Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19

2.4.1 LEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2.4.2 LED Direct Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

2.5 Half Duplex vs. Full Duplex . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

2.6 Internal Loopback . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

2.7 BIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20

3.0 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.1 MII Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

3.1.1 Nibble-wide MII Data Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.1.2 Collision Detect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.1.3 Carrier Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

3.2 Reduced MII Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

3.3 10 Mb Serial Network Interface (SNI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

3.4 802.3u MII Serial Management Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22

3.4.1 Serial Management Register Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.4.2 Serial Management Access Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

3.4.3 Serial Management Preamble Suppression . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

4.0 Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

4.1 100BASE-TX TRANSMITTER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24

4.1.1 Code-group Encoding and Injection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.1.2 Scrambler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.1.3 NRZ to NRZI Encoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.1.4 Binary to MLT-3 Convertor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2 100BASE-TX RECEIVER . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26

4.2.1 Analog Front End . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2.2 Digital Signal Processor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26

4.2.2.1 Digital Adaptive Equalization and Gain Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

4.2.2.2 Base Line Wander Compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.3 Signal Detect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.4 MLT-3 to NRZI Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.5 NRZI to NRZ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.6 Serial to Parallel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

4.2.7 Descrambler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.8 Code-group Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.9 4B/5B Decoder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.10 100BASE-TX Link Integrity Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.2.11 Bad SSD Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

DP83848C

3 www.national.com

4.3 10BASE-T TRANSCEIVER MODULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30

4.3.1 Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

4.3.2 Smart Squelch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.3 Collision Detection and SQE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

DP83848C

4.3.4 Carrier Sense . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.5 Normal Link Pulse Detection/Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

4.3.6 Jabber Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.3.7 Automatic Link Polarity Detection and Correction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.3.8 Transmit and Receive Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.3.9 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

4.3.10 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

5.0 Design Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

5.1 TPI Network Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33

5.2 ESD Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

5.3 Clock In (X1) Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

5.4 Power Feedback Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

5.5 Power Down/Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

5.5.1 Power Down Control Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

5.5.2 Interrupt Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

5.6 Energy Detect Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

6.0 Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

6.1 Hardware Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

6.2 Software Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

7.0 Register Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

7.1 Register Definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41

7.1.1 Basic Mode Control Register (BMCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

7.1.2 Basic Mode Status Register (BMSR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

7.1.3 PHY Identifier Register #1 (PHYIDR1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

7.1.4 PHY Identifier Register #2 (PHYIDR2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

7.1.5 Auto-Negotiation Advertisement Register (ANAR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

7.1.6 Auto-Negotiation Link Partner Ability Register (ANLPAR) (BASE Page) . . . . . . . . . . . . . . . . 47

7.1.7 Auto-Negotiation Link Partner Ability Register (ANLPAR) (Next Page) . . . . . . . . . . . . . . . . . 48

7.1.8 Auto-Negotiate Expansion Register (ANER) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

7.1.9 Auto-Negotiation Next Page Transmit Register (ANNPTR) . . . . . . . . . . . . . . . . . . . . . . . . . . 49

7.2 Extended Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50

7.2.1 PHY Status Register (PHYSTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50

7.2.2 MII Interrupt Control Register (MICR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

7.2.3 MII Interrupt Status and Misc. Control Register (MISR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

7.2.4 False Carrier Sense Counter Register (FCSCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

7.2.5 Receiver Error Counter Register (RECR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

7.2.6 100 Mb/s PCS Configuration and Status Register (PCSR) . . . . . . . . . . . . . . . . . . . . . . . . . . 55

7.2.7 RMII and Bypass Register (RBR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7.2.8 LED Direct Control Register (LEDCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

7.2.9 PHY Control Register (PHYCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

7.2.10 10Base-T Status/Control Register (10BTSCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58

7.2.11 CD Test and BIST Extensions Register (CDCTRL1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60

7.2.12 Energy Detect Control (EDCR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

8.0 Electrical Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

8.1 DC Specs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62

8.2 AC Specs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64

8.2.1 Power Up Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

8.2.2 Reset Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

8.2.3 MII Serial Management Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

8.2.4 100 Mb/s MII Transmit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

8.2.5 100 Mb/s MII Receive Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.2.6 100BASE-TX Transmit Packet Latency Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

8.2.7 100BASE-TX Transmit Packet Deassertion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

8.2.8 100BASE-TX Transmit Timing (tR/F & Jitter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

8.2.9 100BASE-TX Receive Packet Latency Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

8.2.10 100BASE-TX Receive Packet Deassertion Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

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8.2.11 10 Mb/s MII Transmit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

8.2.12 10 Mb/s MII Receive Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71

8.2.13 10 Mb/s Serial Mode Transmit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

8.2.14 10 Mb/s Serial Mode Receive Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

8.2.15 10BASE-T Transmit Timing (Start of Packet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

8.2.16 10BASE-T Transmit Timing (End of Packet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73

8.2.17 10BASE-T Receive Timing (Start of Packet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

8.2.18 10BASE-T Receive Timing (End of Packet) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74

8.2.19 10 Mb/s Heartbeat Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8.2.20 10 Mb/s Jabber Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

8.2.21 10BASE-T Normal Link Pulse Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

8.2.22 Auto-Negotiation Fast Link Pulse (FLP) Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

8.2.23 100BASE-TX Signal Detect Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.2.24 100 Mb/s Internal Loopback Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.2.25 10 Mb/s Internal Loopback Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78

8.2.26 RMII Transmit Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

8.2.27 RMII Receive Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.2.28 Isolation Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

8.2.29 25 MHz_OUT Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

8.2.30 100 Mb/s X1 to TX_CLK Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82

9.0 Physical Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

DP83848C

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List of Figures

Figure 1. DP83848C Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

DP83848C

Figure 2. PHYAD Strapping Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

Figure 3. AN Strapping and LED Loading Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Figure 4. Typical MDC/MDIO Read Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 5. Typical MDC/MDIO Write Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Figure 6. 100BASE-TX Transmit Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

Figure 7. 100BASE-TX Receive Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

Figure 8. EIA/TIA Attenuation vs. Frequency for 0, 50, 100, 130 & 150 meters of CAT 5 cable . . . . . . . . . . . 28

Figure 9. 100BASE-TX BLW Event . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

Figure 10. 10BASE-T Twisted Pair Smart Squelch Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

Figure 11. 10/100 Mb/s Twisted Pair Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Figure 12. Crystal Oscillator Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Figure 13. Power Feeback Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

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List of Tables

Table 1. Auto-Negotiation Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Table 2. PHY Address Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Table 3. LED Mode Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

Table 4. Supported packet sizes at +/-50ppm +/-100ppm for each clock . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Table 5. Typical MDIO Frame Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

Table 5. 4B5B Code-Group Encoding/Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25

Table 6. 25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34

Table 7. 25 MHz Oscillator Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

Table 8. 50 MHz Oscillator Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

Table 9. 25 MHz Crystal Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Table 10. Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

Table 11. Register Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39

Table 12. Basic Mode Control Register (BMCR), address 0x00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42

Table 13. Basic Mode Status Register (BMSR), address 0x01 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .44

Table 14. PHY Identifier Register #1 (PHYIDR1), address 0x02 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Table 15. PHY Identifier Register #2 (PHYIDR2), address 0x03 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

Table 16. Negotiation Advertisement Register (ANAR), address 0x04 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45

Table 17. Auto-Negotiation Link Partner Ability Register (ANLPAR) (BASE Page), address 0x05 . . . . . . . .46

Table 18. Auto-Negotiation Link Partner Ability Register (ANLPAR) (Next Page), address 0x05 . . . . . . . . .48

Table 19. Auto-Negotiate Expansion Register (ANER), address 0x06 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

Table 20. Auto-Negotiation Next Page Transmit Register (ANNPTR), address 0x07 . . . . . . . . . . . . . . . . . . . 49

Table 21. PHY Status Register (PHYSTS), address 0x10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50

Table 22. MII Interrupt Control Register (MICR), address 0x11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52

Table 23. MII Interrupt Status and Misc. Control Register (MISR), address 0x12 . . . . . . . . . . . . . . . . . . . . . . 53

Table 24. False Carrier Sense Counter Register (FCSCR), address 0x14 . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Table 25. Receiver Error Counter Register (RECR), address 0x15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .54

Table 26. 100 Mb/s PCS Configuration and Status Register (PCSR), address 0x16 . . . . . . . . . . . . . . . . . . . .55

Table 27. RMII and Bypass Register (RBR), addresses 0x17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56

Table 28. LED Direct Control Register (LEDCR), address 0x18 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

Table 29. PHY Control Register (PHYCR), address 0x19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

Table 30. 10Base-T Status/Control Register (10BTSCR), address 0x1A . . . . . . . . . . . . . . . . . . . . . . . . . . . . .58

Table 31. CD Test and BIST Extensions Register (CDCTRL1), address 0x1B . . . . . . . . . . . . . . . . . . . . . . . . .60

Table 32. Energy Detect Control (EDCR), address 0x1D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

DP83848C

7 www.national.com

Pin Layout

DP83848C

PFBIN2

RX_CLK

RX_DV/MII_MODE

CRS/CRS_DV/LED_CFG

RX_ER/MDIX_EN

COL/PHYAD0

RXD_0/PHYAD1

RXD_1/PHYAD2

RXD_2/PHYAD3

RXD_3/PHYAD4

IOGND

IOVDD33

DGND

IOGNDX1X2

36

o

35

2

1

37

38

39

40

41

42

43

44

45

46

47

48

IOVDD33

MDC

MDIO

RESET_N

34

33

32

31

30

29

DP83848C

3

4

5

6

7

8

LED_LINK/AN0

LED_SPEED/AN1

28

27

9

10

LED_ACT/COL/AN_EN

25MHz_OUT

26

25

11

12

24

23

22

21

20

19

18

17

16

15

14

13

RBIAS

PFBOUT

AVDD33

RESERVED

RESERVED

AGND

PFBIN1

TD +

TD -

AGND

RD +

RD -

TXD_0

TXD_1

TX_CLK

TX_EN

TXD_2

TXD_3/SNI_MODE

Top View

NS Package Number VBH48A

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RESERVED

PWR_DOWN/INT

RESERVED

RESERVED

RESERVED

RESERVED

1.0 Pin Descriptions

The DP83848C pins are classified into the following inter­face categories (each interface is described in the sections
that follow):

— Serial Management Interface
— MAC Data Interface
— Clock Interface
— LED Interface
— Reset and Power Down
— Strap Options
— 10/100 Mb/s PMD Interface
— Special Connect Pins
— Power and Ground pins
Note: Strapping pin option. Please see Section 1.6 for strap

definitions.

1.1 Serial Management Interface

Signal Name Type Pin # Description

MDC I 31 MANAGEMENT DATA CLOCK: Synchronous clock to the MDIO

MDIO I/O 30 MANAGEMENT DATA I/O: Bi-directional management instruc-

All DP83848C signal pins are I/O cells regardless of the
particular use. The definitions below define the functionality
of the I/O cells for each pin.

Type: I Input
Type: O Output
Type: I/O Input/Output
Type OD Open Drain
Type: PD,PU Internal Pulldown/Pullup
Type: S Strapping Pin (All strap pins have weak in-

ternal pull-ups or pull-downs. If the default
strap value is needed to be changed then an

external 2.2 kΩ resistor should be used.

Please see

management data input/output serial interface which may be
asynchronous to transmit and receive clocks. The maximum clock
rate is 25 MHz with no minimum clock rate.

tion/data signal that may be sourced by the station management

entity or the PHY. This pin requires a 1.5 kΩ pullup resistor.

Section 1.6 for details.)

DP83848C

1.2 MAC Data Interface

Signal Name Type Pin # Description

TX_CLK O 1 MII TRANSMIT CLOCK: 25 MHz Transmit clock output in 100

TX_EN I, PD 2 MII TRANSMIT ENABLE: Active high input indicates the pres-

TXD_0

TXD_1

TXD_2

TXD_3

I

S, I, PD

3

4

5

6

Mb/s mode or 2.5 MHz in 10 Mb/s mode derived from the 25 MHz
reference clock.

Unused in RMII mode. The device uses the X1 reference clock in­put as the 50 MHz reference for both transmit and receive.

SNI TRANSMIT CLOCK: 10 MHz Transmit clock output in 10 Mb
SNI mode. The MAC should source TX_EN and TXD_0 using this
clock.

ence of valid data inputs on TXD[3:0].

RMII TRANSMIT ENABLE: Active high input indicates the pres­ence of valid data on TXD[1:0].

SNI TRANSMIT ENABLE: Active high input indicates the pres­ence of valid data on TXD_0.

MII TRANSMIT DATA: Transmit data MII input pins, TXD[3:0],
that accept data synchronous to the TX_CLK (2.5 MHz in 10 Mb/s
mode or 25 MHz in 100 Mb/s mode).

RMII TRANSMIT DATA: Transmit data RMII input pins, TXD[1:0],
that accept data synchronous to the 50 MHz reference clock.

SNI TRANSMIT DATA: Transmit data SNI input pin, TXD_0, that
accept data synchronous to the TX_CLK (10 MHz in 10 Mb/s SNI
mode).

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Signal Name Type Pin # Description

RX_CLK O 38 MII RECEIVE CLOCK: Provides the 25 MHz recovered receive

DP83848C

RX_DV S, O, PD 39 MII RECEIVE DATA VALID: Asserted high to indicate that valid

RX_ER S, O, PU 41 MII RECEIVE ERROR: Asserted high synchronously to RX_CLK

RXD_0

RXD_1

RXD_2

RXD_3

CRS/CRS_DV S, O, PU 40 MII CARRIER SENSE: Asserted high to indicate the receive me-

COL S, O, PU 42 MII COLLISION DETECT: Asserted high to indicate detection of

S, O, PD 43

44

45

46

clocks for 100 Mb/s mode and 2.5 MHz for 10 Mb/s mode.

Unused in RMII mode. The device uses the X1 reference clock in­put as the 50 MHz reference for both transmit and receive.

SNI RECEIVE CLOCK: Provides the 10 MHz recovered receive
clocks for 10 Mb/s SNI mode.

data is present on the corresponding RXD[3:0]. MII mode by de
fault with internal pulldown.

RMII Synchronous Receive Data Valid: This signal provides the
RMII Receive Data Valid indication independent of Carrier Sense.

This pin is not used in SNI mode.

to indicate that an invalid symbol has been detected within a re­ceived packet in 100 Mb/s mode.

RMII RECEIVE ERROR: Assert high synchronously to X1 when­ever it detects a media error and RXDV is asserted in 100 Mb/s
mode.

This pin is not required to be used by a MAC, in either MII or RMII
mode, since the Phy is required to corrupt data on a receive error.

This pin is not used in SNI mode.

MII RECEIVE DATA: Nibble wide receive data signals driven syn­chronously to the RX_CLK, 25 MHz for 100 Mb/s mode, 2.5 MHz
for 10 Mb/s mode). RXD[3:0] signals contain valid data when
RX_DV is asserted.

RMII RECEIVE DATA: 2-bits receive data signals, RXD[1:0], driv­en synchronously to the X1 clock, 50 MHz.

SNI RECEIVE DATA: Receive data signal, RXD_0, driven syn­chronously to the RX_CLK. RXD_0 contains valid data when CRS
is asserted. RXD[3:1] are not used in this mode.

dium is non-idle.

RMII CARRIER SENSE/RECEIVE DATA VALID: This signal
combines the RMII Carrier and Receive Data Valid indications.
For a detailed description of this signal, see the RMII Specifica
tion.

SNI CARRIER SENSE: Asserted high to indicate the receive me­dium is non-idle. It is used to frame valid receive data on the
RXD_0 signal.

a collision condition (simultaneous transmit and receive activity)
in 10 Mb/s and 100 Mb/s Half Duplex Modes.

While in 10BASE-T Half Duplex mode with heartbeat enabled this

pin is also asserted for a duration of approximately 1µs at the end

of transmission to indicate heartbeat (SQE test).

In Full Duplex Mode, for 10 Mb/s or 100 Mb/s operation, this sig­nal is always logic 0. There is no heartbeat function during 10
Mb/s full duplex operation.

RMII COLLISION DETECT: Per the RMII Specification, no COL
signal is required. The MAC will recover CRS from the CRS_DV
signal and use that along with its TX_EN signal to determine col
lision.

SNI COLLISION DETECT: Asserted high to indicate detection of
a collision condition (simultaneous transmit and receive activity)
in 10 Mb/s SNI mode.

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1.3 Clock Interface

Signal Name Type Pin # Description

X1 I 34 CRYSTAL/OSCILLATOR INPUT: This pin is the primary clock

X2 O 33 CRYSTAL OUTPUT: This pin is the primary clock reference out-

25MHz_OUT O 25 25 MHz CLOCK OUTPUT:

reference input for the DP83848C and must be connected to a 25
MHz 0.005% (
either an external crystal resonator connected across pins X1 and
X2, or an external CMOS-level oscillator source connected to pin
X1 only.

RMII REFERENCE CLOCK: This pin is the primary clock refer­ence input for the RMII mode and must be connected to a 50 MHz

0.005% (

put to connect to an external 25 MHz crystal resonator device.
This pin must be left unconnected if an external CMOS oscillator
clock source is used.

In MII mode, this pin provides a 25 MHz clock output to the sys­tem.

In RMII mode, this pin provides a 50 MHz clock output to the sys­tem.

This allows other devices to use the reference clock from the
DP83848C without requiring additional clock sources.

+50 ppm) clock source. The DP83848C supports

+50 ppm) CMOS-level oscillator source.

DP83848C

1.4 LED Interface

See Table 3 for LED Mode Selection.

Signal Name Type Pin # Description

LED_LINK S, O, PU 28 LINK LED: In Mode 1, this pin indicates the status of the LINK.

LED_SPEED S, O, PU 27 SPEED LED: The LED is ON when device is in 100 Mb/s and OFF

LED_ACT/COL S, O, PU 26 ACTIVITY LED: In Mode 1, this pin is the Activity LED which is

The LED will be ON when Link is good.

LINK/ACT LED: In Mode 2 and Mode 3, this pin indicates transmit
and receive activity in addition to the status of the Link. The LED
will be ON when Link is good. It will blink when the transmitter or
receiver is active.

when in 10 Mb/s. Functionality of this LED is independent of mode
selected.

ON when activity is present on either Transmit or Receive.

COLLISION/DUPLEX LED: In Mode 2, this pin by default indi­cates Collision detection. For Mode 3, this LED output may be
programmed to indicate Full-duplex status instead of Collision.

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1.5 Reset and Power Down

Signal Name Type Pin # Description

DP83848C

RESET_N I, PU 29 RESET: Active Low input that initializes or re-initializes the

PWR_DOWN/INT I, OD, PU 7 See Section 5.5 for detailed description.

DP83848C. Asserting this pin low for at least 1 µs will force a reset

process to occur. All internal registers will re-initialize to their de
fault states as specified for each bit in the Register Block section.
All strap options are re-initialized as well.

The default function of this pin is POWER DOWN.

POWER DOWN: The pin is an active low input in this mode and
should be asserted low to put the device in a Power Down mode.

INTERRUPT: The pin is an open drain output in this mode and will
be asserted low when an interrupt condition occurs. Although the
pin has a weak internal pull-up, some applications may require an
external pull-up resister. Register access is required for the pin to
be used as an interrupt mechanism. See
Mechanism for more details on the interrupt mechanisms.

Section 5.5.2 Interrupt

1.6 Strap Options

The DP83848C uses many of the functional pins as strap options. The values of these pins are sampled during reset and
used to strap the device into specific modes of operation. The strap option pin assignments are defined below. The func
tional pin name is indicated in parentheses.

-

-

A 2.2 kΩ resistor should be used for pull-down or pull-up to change the default strap option. If the default option is

required, then there is no need for external pull-up or pull down resistors. Since these pins may have alternate functions
after reset is deasserted, they should not be connected directly to VCC or GND.

Signal Name Type Pin # Description

PHYAD0 (COL)

PHYAD1 (RXD_0)

PHYAD2 (RXD_1)

PHYAD3 (RXD_2)

PHYAD4 (RXD_3)

S, O, PU

S, O, PD

42

43

44

45

46

PHY ADDRESS [4:0]: The DP83848C provides five PHY ad­dress pins, the state of which are latched into the PHYCTRL reg­ister at system Hardware-Reset.

The DP83848C supports PHY Address strapping values 0
(<00000>) through 31 (<11111>). A PHY Address of 0 puts the
part into the MII Isolate Mode. The MII isolate mode must be se
lected by strapping Phy Address 0; changing to Address 0 by reg­ister write will not put the Phy in the MII isolate mode. Please refer
to section 2.3 for additional information.

PHYAD0 pin has weak internal pull-up resistor.

PHYAD[4:1] pins have weak internal pull-down resistors.

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Signal Name Type Pin # Description

AN_EN (LED_ACT/COL)

AN_1 (LED_SPEED)

AN_0 (LED_LINK)

S, O, PU 26

27

28

Auto-Negotiation Enable: When high, this enables Auto-Negoti­ation with the capability set by ANO and AN1 pins. When low, this
puts the part into Forced Mode with the capability set by AN0 and
AN1 pins.

AN0 / AN1: These input pins control the forced or advertised op­erating mode of the DP83848C according to the following table.
The value on these pins is set by connecting the input pins to
GND (0) or V

NEVER be connected directly to GND or VCC.

The value set at this input is latched into the DP83848C at Hard­ware-Reset.

The float/pull-down status of these pins are latched into the Basic
Mode Control Register and the Auto_Negotiation Advertisement
Register during Hardware-Reset.

The default is 111 since these pins have internal pull-ups.

(1) through 2.2 kΩ resistors. These pins should

CC

AN_EN AN1 AN0 Forced Mode

0 0 0 10BASE-T, Half-Duplex

0 0 1 10BASE-T, Full-Duplex

0 1 0 100BASE-TX, Half-Duplex

0 1 1 100BASE-TX, Full-Duplex

AN_EN AN1 AN0 Advertised Mode

1 0 0 10BASE-T, Half/Full-Duplex

1 0 1 100BASE-TX, Half/Full-Duplex

1 1 0 10BASE-T Half-Duplex

100BASE-TX, Half-Duplex

1 1 1 10BASE-T, Half/Full-Duplex

100BASE-TX, Half/Full-Duplex

DP83848C

MII_MODE (RX_DV)

SNI_MODE (TXD_3)

LED_CFG (CRS) S, O, PU 40 LED CONFIGURATION: This strapping option determines the

MDIX_EN (RX_ER) S, O, PU 41 MDIX ENABLE: Default is to enable MDIX. This strapping option

S, O, PD 39

MII MODE SELECT: This strapping option pair determines the

6

operating mode of the MAC Data Interface. Default operation (No
pull-ups) will enable normal MII Mode of operation. Strapping
MII_MODE high will cause the device to be in RMII or SNI mode
of operation, determined by the status of the SNI_MODE strap.
Since the pins include internal pull-downs, the default values are

0.

The following table details the configurations:

MII_MODE SNI_MODE MAC Interface

Mode

0 X MII Mode

1 0 RMII Mode

1 1 10 Mb SNI Mode

mode of operation of the LED pins. Default is Mode 1. Mode 1 and
Mode 2 can be controlled via the strap option. All modes are con
figurable via register access.

SeeTable 3 for LED Mode Selection.

disables Auto-MDIX. An external pull-down will disable Auto­MDIX mode.

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13 www.national.com

1.7 10 Mb/s and 100 Mb/s PMD Interface

Signal Name Type Pin # Description

DP83848C

TD-, TD+ I/O 16, 17 Differential common driver transmit output (PMD Output Pair).

RD-, RD+ I/O 13, 14 Differential receive input (PMD Input Pair). These differential in-

These differential outputs are automatically configured to either
10BASE-T or 100BASE-TX signaling.

In Auto-MDIX mode of operation, this pair can be used as the Re­ceive Input pair.

These pins require 3.3V bias for operation.

puts are automatically configured to accept either 100BASE-TX
or 10BASE-T signaling.

In Auto-MDIX mode of operation, this pair can be used as the
Transmit Output pair.

These pins require 3.3V bias for operation.

1.8 Special Connections

Signal Name Type Pin # Description

RBIAS I 24 Bias Resistor Connection. A 4.87 kΩ 1% resistor should be con-

nected from RBIAS to GND.

PFBOUT O 23 Power Feedback Output. Parallel caps, 10µ F (Tantalum pre-

PFBIN1

PFBIN2

RESERVED I/O 8, 9, 10, 11, 12RESERVED: These pins must be left unconnected.

I 18

37

ferred) and 0.1µF, should be placed close to the PFBOUT. Con-

nect this pin to PFBIN1 (pin 18) and PFBIN2 (pin 37). See
Section 5.4 for proper placement pin.

Power Feedback Input. These pins are fed with power from
PFBOUT pin. A small capacitor of 0.1
close to each pin.

Note: Do not supply power to these pins other than from
PFBOUT.

µF should be connected

RESERVED I/O 20, 21 RESERVED: These pins must be pulled-up through 2.2 kΩ resis-

tors to AVDD33 supply.

1.9 Power Supply Pins

Signal Name Pin # Description

IOVDD33 32, 48 I/O 3.3V Supply

IOGND 35, 47 I/O Ground

DGND 36 Digital Ground

AVDD33 22 Analog 3.3V Supply

AGND 15, 19 Analog Ground

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1.10 Package Pin Assignments

VBH48A Pin # Pin Name

1 TX_CLK

2 TX_EN

3 TXD_0

4 TXD_1

5 TXD_2

6 TXD_3/SNI_MODE

7 PWR_DOWN/INT

8 RESERVED

9 RESERVED

10 RESERVED

11 RESERVED

12 RESERVED

13 RD -

14 RD +

15 AGND

16 TD -

17 TD +

18 PFBIN1

19 AGND

20 RESERVED

21 RESERVED

22 AVDD33

23 PFBOUT

24 RBIAS

25 25MHz_OUT

26 LED_ACT/COL/AN_EN

27 LED_SPEED/AN1

28 LED_LINK/AN0

29 RESET_N

30 MDIO

31 MDC

32 IOVDD33

33 X2

34 X1

35 IOGND

36 DGND

37 PFBIN2

38 RX_CLK

39 RX_DV/MII_MODE

40 CRS/CRS_DV/LED_CFG

DP83848C

VBH48A Pin # Pin Name

41 RX_ER/MDIX_EN

42 COL/PHYAD0

43 RXD_0/PHYAD1

44 RXD_1/PHYAD2

45 RXD_2/PHYAD3

46 RXD_3/PHYAD4

47 IOGND

48 IOVDD33

15 www.national.com

2.0 Configuration

This section includes information on the various configura­tion options available with the DP83848C. The configura­tion options described below include:

DP83848C

— Auto-Negotiation
— PHY Address and LEDs
— Half Duplex vs. Full Duplex
— Isolate mode
— Loopback mode
—BIST

2.1 Auto-Negotiation

The Auto-Negotiation function provides a mechanism for
exchanging configuration information between two ends of
a link segment and automatically selecting the highest per
formance mode of operation supported by both devices.
Fast Link Pulse (FLP) Bursts provide the signalling used to
communicate Auto-Negotiation abilities between two
devices at each end of a link segment. For further detail
regarding Auto-Negotiation, refer to Clause 28 of the IEEE

802.3u specification. The DP83848C supports four differ
ent Ethernet protocols (10 Mb/s Half Duplex, 10 Mb/s Full
Duplex, 100 Mb/s Half Duplex, and 100 Mb/s Full Duplex),
so the inclusion of Auto-Negotiation ensures that the high
est performance protocol will be selected based on the
advertised ability of the Link Partner. The Auto-Negotiation
function within the DP83848C can be controlled either by
internal register access or by the use of the AN_EN, AN1
and AN0 pins.

2.1.1 Auto-Negotiation Pin Control

The state of AN_EN, AN0 and AN1 determines whether the
DP83848C is forced into a specific mode or Auto-Negotia­tion will advertise a specific ability (or set of abilities) as
given in
be selected without requiring internal register access.

The state of AN_EN, AN0 and AN1, upon power-up/reset,
determines the state of bits [8:5] of the ANAR register.

The Auto-Negotiation function selected at power-up or
reset can be changed at any time by writing to the Basic
Mode Control Register (BMCR) at address 0x00h.

Table 1. These pins allow configuration options to

Tabl e 1. Auto-Negotiation Modes

AN_EN AN1 AN0 Forced Mode

0 0 0 10BASE-T, Half-Duplex

0 0 1 10BASE-T, Full-Duplex

0 1 0 100BASE-TX, Half-Duplex

0 1 1 100BASE-TX, Full-Duplex

AN_EN AN1 AN0 Advertised Mode

1 0 0 10BASE-T, Half/Full-Duplex

1 0 1 100BASE-TX, Half/Full-Duplex

1 1 0 10BASE-T Half-Duplex

100BASE-TX, Half-Duplex

1 1 1 10BASE-T, Half/Full-Duplex

­100BASE-TX, Half/Full-Duplex

2.1.2 Auto-Negotiation Register Control

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When Auto-Negotiation is enabled, the DP83848C trans­mits the abilities programmed into the Auto-Negotiation
Advertisement register (ANAR) at address 04h via FLP

-

Bursts. Any combination of 10 Mb/s, 100 Mb/s, Half­Duplex, and Full Duplex modes may be selected.

Auto-Negotiation Priority Resolution:

— (1) 100BASE-TX Full Duplex (Highest Priority)
— (2) 100BASE-TX Half Duplex
— (3) 10BASE-T Full Duplex
— (4) 10BASE-T Half Duplex (Lowest Priority)
The Basic Mode Control Register (BMCR) at address 00h

provides control for enabling, disabling, and restarting the
Auto-Negotiation process. When Auto-Negotiation is dis
abled, the Speed Selection bit in the BMCR controls
switching between 10 Mb/s or 100 Mb/s operation, and the
Duplex Mode bit controls switching between full duplex
operation and half duplex operation. The Speed Selection
and Duplex Mode bits have no effect on the mode of oper
ation when the Auto-Negotiation Enable bit is set.

The Link Speed can be examined through the PHY Status
Register (PHYSTS) at address 10h after a Link is
achieved.

The Basic Mode Status Register (BMSR) indicates the set
of available abilities for technology types, Auto-Negotiation
ability, and Extended Register Capability. These bits are
permanently set to indicate the full functionality of the
DP83848C (only the 100BASE-T4 bit is not set since the
DP83848C does not support that function).

The BMSR also provides status on:

— Whether or not Auto-Negotiation is complete
— Whether or not the Link Partner is advertising that a re-

mote fault has occurred
— Whether or not valid link has been established
— Support for Management Frame Preamble suppression
The Auto-Negotiation Advertisement Register (ANAR)

indicates the Auto-Negotiation abilities to be advertised by
the DP83848C. All available abilities are transmitted by
default, but any ability can be suppressed by writing to the

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ANAR. Updating the ANAR to suppress an ability is one
way for a management agent to change (restrict) the tech
nology that is used.

The Auto-Negotiation Link Partner Ability Register
(ANLPAR) at address 05h is used to receive the base link
code word as well as all next page code words during the
negotiation. Furthermore, the ANLPAR will be updated to
either 0081h or 0021h for parallel detection to either 100
Mb/s or 10 Mb/s respectively.

The Auto-Negotiation Expansion Register (ANER) indi­cates additional Auto-Negotiation status. The ANER pro­vides status on:

— Whether or not a Parallel Detect Fault has occurred
— Whether or not the Link Partner supports the Next Page

function

— Whether or not the DP83848C supports the Next Page

function

— Whether or not the current page being exchanged by

Auto-Negotiation has been received

— Whether or not the Link Partner supports Auto-Negotia-

tion

2.1.3 Auto-Negotiation Parallel Detection

The DP83848C supports the Parallel Detection function as
defined in the IEEE 802.3u specification. Parallel Detection
requires both the 10 Mb/s and 100 Mb/s receivers to moni
tor the receive signal and report link status to the Auto­Negotiation function. Auto-Negotiation uses this informa
tion to configure the correct technology in the event that the
Link Partner does not support Auto-Negotiation but is
transmitting link signals that the 100BASE-TX or 10BASE­T PMAs recognize as valid link signals.

If the DP83848C completes Auto-Negotiation as a result of
Parallel Detection, bits 5 and 7 within the ANLPAR register
will be set to reflect the mode of operation present in the
Link Partner. Note that bits 4:0 of the ANLPAR will also be
set to 00001 based on a successful parallel detection to
indicate a valid 802.3 selector field. Software may deter
mine that negotiation completed via Parallel Detection by
reading a zero in the Link Partner Auto-Negotiation Able bit
once the Auto-Negotiation Complete bit is set. If configured
for parallel detect mode and any condition other than a sin
gle good link occurs then the parallel detect fault bit will be
set.

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2.1.4 Auto-Negotiation Restart

Once Auto-Negotiation has completed, it may be restarted
at any time by setting bit 9 (Restart Auto-Negotiation) of the
BMCR to one. If the mode configured by a successful Auto­Negotiation loses a valid link, then the Auto-Negotiation
process will resume and attempt to determine the configu
ration for the link. This function ensures that a valid config­uration is maintained if the cable becomes disconnected.

A renegotiation request from any entity, such as a manage­ment agent, will cause the DP83848C to halt any transmit
data and link pulse activity until the break_link_timer
expires (~1500 ms). Consequently, the Link Partner will go
into link fail and normal Auto-Negotiation resumes. The
DP83848C will resume Auto-Negotiation after the
break_link_timer has expired by issuing FLP (Fast Link
Pulse) bursts.

2.1.5 Enabling Auto-Negotiation via Software

It is important to note that if the DP83848C has been initial­ized upon power-up as a non-auto-negotiating device
(forced technology), and it is then required that Auto-Nego­tiation or re-Auto-Negotiation be initiated via software,

12 (Auto-Negotiation Enable) of the Basic Mode Control

bit
Register (BMCR) must first be cleared and then set for any
Auto-Negotiation function to take effect.

2.1.6 Auto-Negotiation Complete Time

Parallel detection and Auto-Negotiation take approximately
2-3 seconds to complete. In addition, Auto-Negotiation with
next page should take approximately 2-3 seconds to com
plete, depending on the number of next pages sent.

Refer to Clause 28 of the IEEE 802.3u standard for a full
description of the individual timers related to Auto-Negotia­tion.

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2.2 Auto-MDIX

When enabled, this function utilizes Auto-Negotiation to
determine the proper configuration for transmission and
reception of data and subsequently selects the appropriate
MDI pair for MDI/MDIX operation. The function uses a ran
dom seed to control switching of the crossover circuitry.
This implementation complies with the corresponding IEEE

802.3 Auto-Negotiation and Crossover Specifications.

Auto-MDIX is enabled by default and can be configured via
strap or via PHYCR (0x19h) register, bits [15:14].

Neither Auto-Negotiation nor Auto-MDIX is required to be
enabled in forcing crossover of the MDI pairs. Forced
crossover can be achieved through the FORCE_MDIX bit,
bit 14 of PHYCR (0x19h) register.

Note: Auto-MDIX will not work in a forced mode of opera­tion.

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DP83848C

17 www.national.com

2.3 PHY Address

The 5 PHY address inputs pins are shared with the
RXD[3:0] pins and COL pin as shown below.

DP83848C

Pin # PHYAD Function RXD Function

The DP83848C can be set to respond to any of 32 possible
PHY addresses via strap pins. The information is latched
into the PHYCR register (address 19h, bits [4:0]) at device
power-up and hardware reset. The PHY Address pins are
shared with the RXD and COL pins. Each DP83848C or
port sharing an MDIO bus in a system must have a unique
physical address.

The DP83848C supports PHY Address strapping values 0
(<0 0 0 0 0 >) throug h 3 1 (<11111>). Strappi n g PHY Address
0 puts the part into Isolate Mode. It should also be noted
that selecting PHY Address 0 via an MDIO write to PHYCR
will not put the device in Isolate Mode. See
more information.

For further detail relating to the latch-in timing requirements
of the PHY Address pins, as well as the other hardware
configuration pins, refer to the Reset summary in
Section 6.0.

Tabl e 2. PHY Address Mapping

42 PHYAD0 COL

43 PHYAD1 RXD_0

44 PHYAD2 RXD_1

45 PHYAD3 RXD_2

46 PHYAD4 RXD_3

Section 2.3.1for

Since the PHYAD[0] pin has weak internal pull-up resistor
and PHYAD[4:1] pins have weak internal pull-down resis
tors, the default setting for the PHY address is 00001
(01h).

Refer to Figure 2 for an example of a PHYAD connection to
external components. In this example, the PHYAD strap­ping results in address 00011 (03h).

2.3.1 MII Isolate Mode

The DP83848C can be put into MII Isolate mode by writing
to bit 10 of the BMCR register or by strapping in Physical
Address 0. It should be noted that selecting Physical
Address 0 via an MDIO write to PHYCR will not put the
device in the MII isolate mode.

When in the MII isolate mode, the DP83848C does not
respond to packet data present at TXD[3:0], TX_EN inputs
and presents a high impedance on the TX_CLK, RX_CLK,
RX_DV, RX_ER, RXD[3:0], COL, and CRS outputs. When
in Isolate mode, the DP83848C will continue to respond to
all management transactions.

While in Isolate mode, the PMD output pair will not transmit
packet data but will continue to source 100BASE-TX
scrambled idles or 10BASE-T normal link pulses.

The DP83848C can Auto-Negotiate or parallel detect to a
specific technology depending on the receive signal at the
PMD input pair. A valid link can be established for the
receiver even when the DP83848C is in Isolate mode.

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RXD_3

PHYAD4= 0

RXD_2

Figure 2. PHYAD Strapping Example

RXD_1

PHYAD2 = 0PHYAD3 = 0

RXD_0

PHYAD1 = 1

2.2kΩ

COL

PHYAD0 = 1

VCC

www.national.com 18

2.4 LED Interface

The DP83848C supports three configurable Light Emitting
Diode (LED) pins. The device supports three LED configu
rations: Link, Speed, Activity and Collision. Function are

Tab le 3. LED Mode Select

Mode LED_CFG[1]

(bit 6)

1 don’t care 1 ON for Good Link

2 0 0 ON for Good Link

3 1 0 ON for Good Link

LED_CFG[0]

(bit 5)

or (pin40)

LED_LINK LED_SPEED LED_ACT/COL

OFF for No Link

BLINK for Activity

BLINK for Activity

multiplexed among the LEDs. The PHY Control Register
(PHYCR) for the LEDs can also be selected through

­address 19h, bits [6:5].

See Table 3 for LED Mode selection.

ON in 100 Mb/s

OFF in 10 Mb/s

ON in 100 Mb/s

OFF in 10 Mb/s

ON in 100 Mb/s

OFF in 10 Mb/s

ON for Activity

OFF for No Activity

ON for Collision

OFF for No Collision

ON for Full Duplex

OFF for Half Duplex

DP83848C

The LED_LINK pin in Mode 1 indicates the link status of
the port. In 100BASE-T mode, link is established as a
result of input receive amplitude compliant with the TP­PMD specifications which will result in internal generation
of signal detect. A 10 Mb/s Link is established as a result of
the reception of at least seven consecutive normal Link
Pulses or the reception of a valid 10BASE-T packet. This
will cause the assertion of LED_LINK. LED_LINK will deas
sert in accordance with the Link Loss Timer as specified in
the IEEE 802.3 specification.

The LED_LINK pin in Mode 1 will be OFF when no LINK is
present.

The LED_LINK pin in Mode 2 and Mode 3 will be ON to
indicate Link is good and BLINK to indicate activity is
present on either transmit or receive activity.

The LED_SPEED pin indicates 10 or 100 Mb/s data rate of
the port. The standard CMOS driver goes high when oper­ating in 100 Mb/s operation. The functionality of this LED is
independent of mode selected.

The LED_ACT/COL pin in Mode 1 indicates the presence
of either transmit or receive activity. The LED will be ON for
Activity and OFF for No Activity. In Mode 2, this pin indi
cates the Collision status of the port. The LED will be ON
for Collision and OFF for No Collision.

The LED_ACT/COL pin in Mode 3 indicates the presence
of Duplex status for 10 Mb/s or 100 Mb/s operation. The
LED will be ON for Full Duplex and OFF for Half Duplex.

In 10 Mb/s half duplex mode, the collision LED is based on
the COL signal.

Since these LED pins are also used as strap options, the
polarity of the LED is dependent on whether the pin is
pulled up or down.

-

-

Specifically, when the LED outputs are used to drive LEDs
directly, the active state of each output driver is dependent
on the logic level sampled by the corresponding AN input
upon power-up/reset. For example, if a given AN input is
resistively pulled low then the corresponding output will be
configured as an active high driver. Conversely, if a given
AN input is resistively pulled high, then the corresponding
output will be configured as an active low driver.

Refer to Figure 3 for an example of AN connections to
external components. In this example, the AN strapping
results in Auto-Negotiation with 10/100 Half/Full-Duplex
advertised.

The adaptive nature of the LED outputs helps to simplify
potential implementation issues of these dual purpose pins.

LED_ACT/COL

AN_EN = 1

2.2kΩ

LED_SPEED
AN1 = 1

2.2kΩ

110Ω

110Ω

2.2kΩ

LED_LINK
AN0 = 1

110Ω

VCC

2.4.1 LEDs

Since the Auto-Negotiation (AN) strap options share the
LED output pins, the external components required for
strapping and LED usage must be considered in order to
avoid contention.

Figure 3. AN Strapping and LED Loading Example

19 www.national.com

2.4.2 LED Direct Control

The DP83848C provides another option to directly control
any or all LED outputs through the LED Direct Control Reg
ister (LEDCR), address 18h. The register does not provide

DP83848C

read access to LEDs.

2.5 Half Duplex vs. Full Duplex

The DP83848C supports both half and full duplex opera­tion at both 10 Mb/s and 100 Mb/s speeds.

Half-duplex relies on the CSMA/CD protocol to handle colli­sions and network access. In Half-Duplex mode, CRS
responds to both transmit and receive activity in order to
maintain compliance with the IEEE 802.3 specification.

Since the DP83848C is designed to support simultaneous
transmit and receive activity it is capable of supporting full­duplex switched applications with a throughput of up to 200
Mb/s per port when operating in 100BASE-TX mode.
Because the CSMA/CD protocol does not apply to full­duplex operation, the DP83848C disables its own internal
collision sensing and reporting functions and modifies the
behavior of Carrier Sense (CRS) such that it indicates only
receive activity. This allows a full-duplex capable MAC to
operate properly.

All modes of operation (100BASE-TX and 10BASE-T) can
run either half-duplex or full-duplex. Additionally, other than
CRS and Collision reporting, all remaining MII signaling
remains the same regardless of the selected duplex mode.

It is important to understand that while Auto-Negotiation
with the use of Fast Link Pulse code words can interpret
and configure to full-duplex operation, parallel detection
can not recognize the difference between full and half­duplex from a fixed 10 Mb/s or 100 Mb/s link partner over
twisted pair. As specified in the 802.3u specification, if a
far-end link partner is configured to a forced full duplex
100BASE-TX ability, the parallel detection state machine in
the partner would be unable to detect the full duplex capa
bility of the far-end link partner. This link segment would
negotiate to a half duplex 100BASE-TX configuration
(same scenario for 10 Mb/s).

2.6 Internal Loopback

The DP83848C includes a Loopback Test mode for facili-

-

tating system diagnostics. The Loopback mode is selected
through bit 14 (Loopback) of the Basic Mode Control Reg
ister (BMCR). Writing 1 to this bit enables MII transmit data
to be routed to the MII receive outputs. Loopback status
may be checked in bit 3 of the PHY Status Register
(PHYSTS). While in Loopback mode the data will not be
transmitted onto the media. To ensure that the desired
operating mode is maintained, Auto-Negotiation should be
disabled before selecting the Loopback mode.

2.7 BIST

The DP83848C incorporates an internal Built-in Self Test
(BIST) circuit to accommodate in-circuit testing or diagnos
tics. The BIST circuit can be utilized to test the integrity of
the transmit and receive data paths. BIST testing can be
performed with the part in the internal loopback mode or
externally looped back using a loopback cable fixture.

The BIST is implemented with independent transmit and
receive paths, with the transmit block generating a continu­ous stream of a pseudo random sequence. The user can
select a 9 bit or 15 bit pseudo random sequence from the
PSR_15 bit in the PHY Control Register (PHYCR). The
received data is compared to the generated pseudo-ran
dom data by the BIST Linear Feedback Shift Register
(LFSR) to determine the BIST pass/fail status.

The pass/fail status of the BIST is stored in the BIST status
bit in the PHYCR register. The status bit defaults to 0 (BIST
fail) and will transition on a successful comparison. If an
error (mis-compare) occurs, the status bit is latched and is
cleared upon a subsequent write to the Start/Stop bit.

For transmit VOD testing, the Packet BIST Continuous
Mode can be used to allow continuous data transmission,
setting BIST_CONT_MODE, bit 5, of CDCTRL1 (0x1Bh).

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The number of BIST errors can be monitored through the
BIST Error Count in the CDCTRL1 (0x1Bh), bits [15:8].

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www.national.com 20

3.0 Functional Description

The DP83848C supports several modes of operation using
the MII interface pins. The options are defined in the follow
ing sections and include:

— MII Mode
— RMII Mode
— 10 Mb Serial Network Interface (SNI)
The modes of operation can be selected by strap options

or register control. For RMII mode, it is required to use the
strap option, since it requires a 50 MHz clock instead of the
normal 25 MHz.

In each of these modes, the IEEE 802.3 serial manage­ment interface is operational for device configuration and
status. The serial management interface of the MII allows
for the configuration and control of multiple PHY devices,
gathering of status, error information, and the determina
tion of the type and capabilities of the attached PHY(s).

3.1 MII Interface

The DP83848C incorporates the Media Independent Inter­face (MII) as specified in Clause 22 of the IEEE 802.3u
standard. This interface may be used to connect PHY
devices to a MAC in 10/100 Mb/s systems. This section
describes the nibble wide MII data interface.

The nibble wide MII data interface consists of a receive bus
and a transmit bus each with control signals to facilitate
data transfer between the PHY and the upper layer (MAC).

3.1.1 Nibble-wide MII Data Interface

Clause 22 of the IEEE 802.3u specification defines the
Media Independent Interface. This interface includes a
dedicated receive bus and a dedicated transmit bus. These
two data buses, along with various control and status sig
nals, allow for the simultaneous exchange of data between
the DP83848C and the upper layer agent (MAC).

The receive interface consists of a nibble wide data bus
RXD[3:0], a receive error signal RX_ER, a receive data
valid flag RX_DV, and a receive clock RX_CLK for syn
chronous transfer of the data. The receive clock operates
at either 2.5 MHz to support 10 Mb/s operation modes or at
25 MHz to support 100 Mb/s operational modes.

The transmit interface consists of a nibble wide data bus
TXD[3:0], a transmit enable control signal TX_EN, and a
transmit clock TX_CLK which runs at either 2.5 MHz or 25
MHz.

Additionally, the MII includes the carrier sense signal CRS,
as well as a collision detect signal COL. The CRS signal
asserts to indicate the reception of data from the network
or as a function of transmit data in Half Duplex mode. The
COL signal asserts as an indication of a collision which can
occur during half-duplex operation when both a transmit
and receive operation occur simultaneously.

3.1.2 Collision Detect

For Half Duplex, a 10BASE-T or 100BASE-TX collision is
detected when the receive and transmit channels are
active simultaneously. Collisions are reported by the COL
signal on the MII.

-

-

-

-

If the DP83848C is transmitting in 10 Mb/s mode when a
collision is detected, the collision is not reported until seven
bits have been received while in the collision state. This
prevents a collision being reported incorrectly due to noise
on the network. The COL signal remains set for the dura
tion of the collision.

If a collision occurs during a receive operation, it is immedi­ately reported by the COL signal.

When heartbeat is enabled (only applicable to 10 Mb/s
operation), approximately 1
each packet, a Signal Quality Error (SQE) signal of approx
imately 10 bit times is generated (internally) to indicate
successful transmission. SQE is reported as a pulse on the
COL signal of the MII.

3.1.3 Carrier Sense

Carrier Sense (CRS) is asserted due to receive activity,
once valid data is detected via the squelch function during
10 Mb/s operation. During 100 Mb/s operation CRS is
asserted when a valid link (SD) and two non-contiguous
zeros are detected on the line.

For 10 or 100 Mb/s Half Duplex operation, CRS is asserted
during either packet transmission or reception.

For 10 or 100 Mb/s Full Duplex operation, CRS is asserted
only due to receive activity.

CRS is deasserted following an end of packet.

µs after the transmission of

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3.2 Reduced MII Interface

The DP83848C incorporates the Reduced Media Indepen­dent Interface (RMII) as specified in the RMII specification
(rev1.2) from the RMII Consortium. This interface may be
used to connect PHY devices to a MAC in 10/100 Mb/s
systems using a reduced number of pins. In this mode,
data is transferred 2-bits at a time using the 50 MHz
RMII_REF clock for both transmit and receive. The follow
ing pins are used in RMII mode:

— TX_EN
—TXD[1:0]
— RX_ER (optional for Mac)
— CRS_DV
— RXD[1:0]
— X1 (RMII Reference clock is 50 MHz)
In addition, the RMII mode supplies an RX_DV signal

which allows for a simpler method of recovering receive
data without having to separate RX_DV from the CRS_DV
indication. This is especially useful for systems which do
not require CRS, such as systems that only support full­duplex operation. This signal is also useful for diagnostic
testing where it may be desirable to loop Receive RMII
data directly to the transmitter.

Since the reference clock operates at 10 times the data
rate for 10 Mb/s operation, transmit data is sampled every
10 clocks. Likewise, receive data will be generated every
10th clock so that an attached device can sample the data
every 10 clocks.

RMII mode requires a 50 MHz oscillator be connected to
the device X1 pin. A 50 MHz crystal is not supported.

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DP83848C

21 www.national.com

To tolerate potential frequency differences between the 50
MHz reference clock and the recovered receive clock, the
receive RMII function includes a programmable elasticity
buffer. The elasticity buffer is programmable to minimize
propagation delay based on expected packet size and

DP83848C

clock accuracy. This allows for supporting a range of
packet sizes including jumbo frames.

Table 4. Supported packet sizes at +/-50ppm +/-100ppm for each clock

Start Threshold

RBR[1:0]

1 (4-bits) 2 bits 2400 bytes 1200 bytes

2 (8-bits) 6 bits 7200 bytes 3600 bytes

3 (12-bits) 10 bits 12000 bytes 6000 bytes

0 (16-bits) 14 bits 16800 bytes 8400 bytes

Latency Tolerance Recommended Packet Size

The elasticity buffer will force Frame Check Sequence
errors for packets which overrun or underrun the FIFO.
Underrun and Overrun conditions can be reported in the
RMII and Bypass Register (RBR). The following table indi
cates how to program the elasticity buffer fifo (in 4-bit incre­ments) based on expected max packet size and clock
accuracy. It assumes both clocks (RMII Reference clock
and far-end Transmitter clock) have the same accuracy.

at +/- 50ppm

Recommended Packet Size

at +/- 100ppm

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3.3 10 Mb Serial Network Interface (SNI)

The DP83848C incorporates a 10 Mb Serial Network Inter­face (SNI) which allows a simple serial data interface for 10
Mb only devices. This is also referred to as a 7-wire inter­face. While there is no defined standard for this interface, it
is based on early 10 Mb physical layer devices. Data is
clocked serially at 10 MHz using separate transmit and
receive paths. The following pins are used in SNI mode:

—TX_CLK
—TX_EN
—TXD[0]
—RX_CLK
—RXD[0]
— CRS
—COL

3.4 802.3u MII Serial Management Interface

3.4.1 Serial Management Register Access

The serial management MII specification defines a set of
thirty-two 16-bit status and control registers that are acces
sible through the management interface pins MDC and
MDIO. The DP83848C implements all the required MII reg
isters as well as several optional registers. These registers
are fully described in Section 7.0. A description of the serial
management access protocol follows.

3.4.2 Serial Management Access Protocol

The serial control interface consists of two pins, Manage­ment Data Clock (MDC) and Management Data Input/Out­put (MDIO). MDC has a maximum clock rate of 25 MHz
and no minimum rate. The MDIO line is bi-directional and
may be shared by up to 32 devices. The MDIO frame for
mat is shown below in Tab le 5 .

The MDIO pin requires a pull-up resistor (1.5 kΩ) which,

during IDLE and turnaround, will pull MDIO high. In order to
initialize the MDIO interface, the station management entity
sends a sequence of 32 contiguous logic ones on MDIO to
provide the DP83848C with a sequence that can be used
to establish synchronization. This preamble may be gener
ated either by driving MDIO high for 32 consecutive MDC
clock cycles, or by simply allowing the MDIO pull-up resis
tor to pull the MDIO pin high during which time 32 MDC
clock cycles are provided. In addition 32 MDC clock cycles
should be used to re-sync the device if an invalid start,
opcode, or turnaround bit is detected.

The DP83848C waits until it has received this preamble
sequence before responding to any other transaction.
Once the DP83848C serial management port has been ini
tialized no further preamble sequencing is required until
after a power-on/reset, invalid Start, invalid Opcode, or
invalid turnaround bit has occurred.

The Start code is indicated by a <01> pattern. This assures
the MDIO line transitions from the default idle line state.

Turnaround is defined as an idle bit time inserted between
the Register Address field and the Data field. To avoid con­tention during a read transaction, no device shall actively
drive the MDIO signal during the first bit of Turnaround.
The addressed DP83848C drives the MDIO with a zero for
the second bit of turnaround and follows this with the

­required data.
between MDC and the MDIO as driven/received by the Sta-

­tion (STA) and the DP83848C (PHY) for a typical register
read access.

For write transactions, the station management entity
writes data to the addressed DP83848C thus eliminating
the requirement for MDIO Turnaround. The Turnaround
time is filled by the management entity by inserting <10>.
Figure 5 shows the timing relationship for a typical MII reg­ister write access.

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Figure 4 shows the timing relationship

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www.national.com 22

Table 5. Typical MDIO Frame Format

MII Management

<idle><start><op code><device addr><reg addr><turnaround><data><idle>

Serial Protocol

Read Operation <idle><01><10><AAAAA><RRRRR><Z0><xxxx xxxx xxxx xxxx><idle>

Write Operation <idle><01><01><AAAAA><RRRRR><10><xxxx xxxx xxxx xxxx><idle>

MDC

DP83848C

MDIO

(STA)

MDIO

(PHY)

Z

Z

00011 110000 000

Idle Start

Opcode

(Read)

PHY Address

(PHYAD = 0Ch)

Register Address

(00h = BMCR)

Z

Z

Figure 4. Typical MDC/MDIO Read Operation

MDC

MDIO

(STA)

Z

00011110000000

Idle Start

Opcode

(Write)

PHY Address

(PHYAD = 0Ch)

Register Address

(00h = BMCR)

Figure 5. Typical MDC/MDIO Write Operation

3.4.3 Serial Management Preamble Suppression

The DP83848C supports a Preamble Suppression mode
as indicated by a one in bit 6 of the Basic Mode Status
Register (BMSR, address 01h.) If the station management
entity (i.e. MAC or other management controller) deter
mines that all PHYs in the system support Preamble Sup­pression by returning a one in this bit, then the station
management entity need not generate preamble for each
management transaction.

The DP83848C requires a single initialization sequence of
32 bits of preamble following hardware/software reset. This

Z

Z

0 0 011000100000000

TA

0 0 0 000 00000000

1000

TA

Register Data

Register Data

Z

Idle

ZZ

Z

Idle

requirement is generally met by the mandatory pull-up
resistor on MDIO in conjunction with a continuous MDC, or
the management access made to determine whether Pre
amble Suppression is supported.

While the DP83848C requires an initial preamble

­sequence of 32 bits for management initialization, it does

not require a full 32-bit sequence between each subse
quent transaction. A minimum of one idle bit between man-
agement transactions is required as specified in the IEEE

802.3u specification.

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23 www.national.com

4.0 Architecture

This section describes the operations within each trans­ceiver module, 100BASE-TX and 10BASE-T. Each opera­tion consists of several functional blocks and described in

DP83848C

the following:

— 100BASE-TX Transmitter
— 100BASE-TX Receiver
— 10BASE-T Transceiver Module

4.1 100BASE-TX TRANSMITTER

The 100BASE-TX transmitter consists of several functional
blocks which convert synchronous 4-bit nibble data, as pro
vided by the MII, to a scrambled MLT-3 125 Mb/s serial
data stream. Because the 100BASE-TX TP-PMD is inte­grated, the differential output pins, PMD Output Pair, can
be directly routed to the magnetics.

The block diagram in Figure 6. provides an overview of
each functional block within the 100BASE-TX transmit sec­tion.

The Transmitter section consists of the following functional
blocks:

— Code-group Encoder and Injection block
— Scrambler block (bypass option)
— NRZ to NRZI encoder block
— Binary to MLT-3 converter / Common Driver
The bypass option for the functional blocks within the

100BASE-TX transmitter provides flexibility for applications
where data conversion is not always required. The
DP83848C implements the 100BASE-TX transmit state

­machine diagram as specified in the IEEE 802.3u Stan

dard, Clause 24.

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125MHZ CLOCK

BP_SCR

100BASE-TX

LOOPBACK

TX_CLK

DIVIDE

BY 5

MLT[1:0]

TXD[3:0] /

TX_EN

4B5B CODE-

GROUP

ENCODER &

5B PARALLEL

TO SERIAL

SCRAMBLER

MUX

NRZ TO NRZI

ENCODER

BINARY

TO MLT-3 /

COMMON

DRIVER

Figure 6. 100BASE-TX Transmit Block Diagram

www.national.com 24

PMD OUTPUT PAIR

Table 5. 4B5B Code-Group Encoding/Decoding

6.

DATA CODES

0 11110 0000

1 01001 0001

2 10100 0010

3 10101 0011

4 01010 0100

5 01011 0101

6 01110 0110

7 01111 0111

8 10010 1000

9 10011 1001

A 10110 1010

B 10111 1011

C 11010 1100

D 11011 1101

E 11100 1110

F 11101 1111

IDLE AND CONTROL CODES

H 00100 HALT code-group - Error code

I 11111 Inter-Packet IDLE - 0000 (Note 1)

J 11000 First Start of Packet - 0101 (Note 1)

K 10001 Second Start of Packet - 0101 (Note 1)

T 01101 First End of Packet - 0000 (Note 1)

R 00111 Second End of Packet - 0000 (Note 1)

INVALID CODES

V 00000

V 00001

V 00010

V 00011

V 00101

V 00110

V 01000

V 01100

Note: Control code-groups I, J, K, T and R in data fields will be mapped as invalid codes, together with RX_ER as­serted.

DP83848C

25 www.national.com

4.1.1 Code-group Encoding and Injection

The code-group encoder converts 4-bit (4B) nibble data
generated by the MAC into 5-bit (5B) code-groups for
transmission. This conversion is required to allow control

DP83848C

data to be combined with packet data code-groups. Refer

Table 5 for 4B to 5B code-group mapping details.

to

The code-group encoder substitutes the first 8-bits of the
MAC preamble with a J/K code-group pair (11000 10001)
upon transmission. The code-group encoder continues to
replace subsequent 4B preamble and data nibbles with
corresponding 5B code-groups. At the end of the transmit
packet, upon the deassertion of Transmit Enable signal
from the MAC, the code-group encoder injects the T/R
code-group pair (01101 00111) indicating the end of the
frame.

After the T/R code-group pair, the code-group encoder
continuously injects IDLEs into the transmit data stream
until the next transmit packet is detected (reassertion of
Transmit Enable).

4.1.2 Scrambler

The scrambler is required to control the radiated emissions
at the media connector and on the twisted pair cable (for
100BASE-TX applications). By scrambling the data, the
total energy launched onto the cable is randomly distrib
uted over a wide frequency range. Without the scrambler,
energy levels at the PMD and on the cable could peak
beyond FCC limitations at frequencies related to repeating
5B sequences (i.e., continuous transmission of IDLEs).

The scrambler is configured as a closed loop linear feed­back shift register (LFSR) with an 11-bit polynomial. The
output of the closed loop LFSR is X-ORd with the serial
NRZ data from the code-group encoder. The result is a
scrambled data stream with sufficient randomization to
decrease radiated emissions at certain frequencies by as
much as 20 dB. The DP83848C uses the PHY_ID (pins
PHYAD [4:0]) to set a unique seed value.

transmit transformer primary winding, resulting in a MLT-3
signal.

The 100BASE-TX MLT-3 signal sourced by the PMD Out­put Pair common driver is slew rate controlled. This should
be considered when selecting AC coupling magnetics to
ensure TP-PMD Standard compliant transition times (3 ns
< Tr < 5 ns).

The 100BASE-TX transmit TP-PMD function within the
DP83848C is capable of sourcing only MLT-3 encoded
data. Binary output from the PMD Output Pair is not possi
ble in 100 Mb/s mode.

4.2 100BASE-TX RECEIVER

The 100BASE-TX receiver consists of several functional
blocks which convert the scrambled MLT-3 125 Mb/s serial
data stream to synchronous 4-bit nibble data that is pro
vided to the MII. Because the 100BASE-TX TP-PMD is

integrated, the differential input pins, RD±, can be directly

routed from the AC coupling magnetics.

See Figure 7 for a block diagram of the 100BASE-TX
receive function. This provides an overview of each func­tional block within the 100BASE-TX receive section.

The Receive section consists of the following functional
blocks:

­— Analog Front End

— Digital Signal Processor
— Signal Detect
— MLT-3 to Binary Decoder
— NRZI to NRZ Decoder
— Serial to Parallel
— Descrambler
— Code Group Alignment
—4B/5B Decoder
— Link Integrity Monitor
— Bad SSD Detection

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4.1.3 NRZ to NRZI Encoder

After the transmit data stream has been serialized and
scrambled, the data must be NRZI encoded in order to
comply with the TP-PMD standard for 100BASE-TX trans
mission over Category-5 Unshielded twisted pair cable.

4.1.4 Binary to MLT-3 Convertor

The Binary to MLT-3 conversion is accomplished by con­verting the serial binary data stream output from the NRZI
encoder into two binary data streams with alternately
phased logic one events. These two binary streams are
then fed to the twisted pair output driver which converts the
voltage to current and alternately drives either side of the

www.national.com 26

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4.2.1 Analog Front End

In addition to the Digital Equalization and Gain Control, the
DP83848C includes Analog Equalization and Gain Control
in the Analog Front End. The Analog Equalization reduces
the amount of Digital Equalization required in the DSP.

4.2.2 Digital Signal Processor

The Digital Signal Processor includes Adaptive Equaliza­tion with Gain Control and Base Line Wander Compensa­tion.