Datasheet TU25C256SI, TU25C256SC-2.7, TU25C256SC, TU25C256PI-2.7, TU25C256PI Datasheet (Turbo IC)

CMOS SPI BUS

256K ELECTRICALLY ERASABLE PROGRAMMABLE ROM

32K X 8 BIT EEPROM

Turbo IC, Inc.

25C256

PRELIMINARY INFORMATION

DESCRIPTION:

The Turbo IC 25C256 is a serial 256K EEPROM fabricated
with Turbo’s proprietary, high reliability, high performance
CMOS technology. It’s 256K of memory is organized as
32768 x 8 bits. This de vice off ers a fle xible b yte write and a
faster 64-byte page write. It also offers significant advan­tages in low power and low VCC voltage applications.

The Turbo IC 25C256 is assembled in either a 8-pin PDIP
or 8-pin SOIC package. Pin #1 is the Chip Select (CS). Pin
#2 is the Serial Output (SO). Pin #3 is Write Protect (WP).
Pin #4 is the ground (Vss). Pin #5 is the Serial Input (SI).
Pin #6 is the serial clock (SCK). Pin #7 is the Hold Input
(HOLD)., and Pin #8 is the power supply (Vcc) pin.

The Turbo IC 25C256 uses the Serial Peripheral Interface
(SPI), allowing operation on a three-wire bus. The Turbo IC
25C256 has separate data input (SI) and data output (SO)
pins. The serial clock (SCK) pin controls the data transfer .
Access to the device is controlled through the chip select
(CS) input.

The Turbo IC 25C256 provides the block write inhibit fea­ture where the user has the option of inhibiting writes to 3
different sizes of the memory array. A write protect (WP)
pin is provided to prevent inadver tent writes to the status
register. The Turbo 25C256 can also be put on hold during
any serial communication by asserting the hold (HOLD) pin.

FEA TURES :

• Extended Pow er Supply Voltage
Single Vcc f or Read and Prog ramming
(Vcc = 2.7V to 3.6 V) (Vcc = 4.5V to 5.5V)

• Low P o w er (Isb = 2µa @ 5.5 V)

• SPI (Serial Peripheral Interface) Bus

• Support Byte Write and Page Write (64 Bytes)

• Automatic 64 Byte Page write Operation (max. 10 ms)
Internal Control Timer
Internal Data Latches for 64 Bytes

• Hardware Data Protection by Write Protect Pin

• High Reliability CMOS Technology with Self Redundant

EEPROM Cell

Endurance : 1,000,000 Cycles
Data Retention : 100 Years

• Support SPI Modes 0 (0,0) and 3 (1,1)

• 5.0 Mhz clock rate

PIN DESCRIPTION

SERIAL DATA CLOCK (SCK)

The SCK input pin controls the serial bus timing
of the data transfer that occurs on the serial in­put pin and the serial output pin.

DA T A TRANSFER P AUSE (HOLD)

The HOLD input pin pauses the data transfer,
allowing the host to service higher-priority inter­rupts. Once the device is selected and serial
communication between the controller and the
device is under way, a high to low transition on
HOLD while SCK is low freezes the serial com­munication. Transitions on the SI and SCK pins
are ignored, and the SO pin is at high imped­ance. To resume the serial communication,
HOLD is set high while SCK is low. The serial
sequence restarts from where it had stopped with
no loss of continuity. HOLD should always be
high during normal operation.

WRITE PROTECT (WP)

The WP input pin controls the status register write
protect feature. For normal read and write op­erations, the WP pin is held high. When the WP
pin is low and the WPEN bit in the status register
is "1", all write operations to the status register
are inhibited. The WP pin function is blocked
when the WPEN bit is "0". This feature allows a
user to install the Turbo IC 25C256 into a system
with the WP pin tied to ground and still be able to
program the status register. The WP pin func­tion will then be enabled when the WPEN bit is
set to "1".

SERIAL DATA INPUT (SI)
The SI input pin accepts all opcodes, addresses,
and write data to be input into the Turbo IC
25C256. The data is latched on the rising edge
of the serial clock.

PIN DESCRIPTION

CHIP SELECT (CS)

The CS input pin selects the Turbo IC 25C256.
A high to low transition on CS selects the Turbo
IC 25C256, and keeping CS low keeps the de­vice activated. When CS is brought high, the
Turbo IC 25C256 is deselected and the serial
output pin (SO) is at high impedance.

SERIAL DATA OUTPUT (SO)

The serial output pin is a push-pull serial data
output. During read, the data is shifted out onto
SO on the falling edge of the serial clock.

1

1
2
3
4

5

6

7

8

CS
SO

WP

GND

VCC
HOLD
SCK
SI

8 pin PDIP

1
2
3
4

5

6

7

8

CS
SO

WP

GND

VCC
HOLD
SCK
SI

8 pin SOIC

25C256

PRELIMINARY INFORMATION

Turbo IC, Inc.

DEVICE OPERA TION

The Turbo IC 25C256 has an 8-bit instruction register and an
8-bit status register. The instruction register stores one of the
operation codes defined in Table 1.

T a ble 1. Operation Codes

---------------------------------------------------------------------------------------------

Instruction Operation Operation
Name Code Description

--------------------------------------------------------------------------------------------­ WREN 00000110 Set Write Enable Latch
WRDI 00000100 Reset Write Enable Latch
RDSR 00000101 Read Status Register
WRSR 00000001 Write Status Register
READ 00000011 Read Data from Memory Array
WRITE 00000010 Write Data to Memory Array

In SPI bus convention, the master pro vides the serial cloc k
and initiates the data transfer . The Turbo IC 25C256 are the slave
devices in all applications. The master selects the Turbo IC 25C256
by pulling CS of the device low. Once the device is active , the
master sends the operation code into the instruction register.
The write enable latch is cleared upon po wer up and at the
end of the write cycle of a write instruction. Theref ore , the
WREN instruction precedes all write instructions because the
write enable latch must be set before a write can be executed.
The WRDI instruction is used to clear the write enable latch
through software.

The status register giv es the current oper ation status of the
Turbo IC 25C256. The contents of the status register is given in
Table 2.
Table 2 Status Register Contents

---------------------------------------------------------------------------------­ Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

---------------------------------------------------------------------------------­ WPEN X X X BP1 BP0 WEN BSY

----------------------------------------------------------------------------------

2

25C256

PRELIMINARY INFORMATION

Turbo IC, Inc.

Where, WPEN is the write protect enable bit. Setting WPEN to a
"1" enables the hardware write protect, and a "0"
disables the hardware write protect. This bit is

non-volatile and is programmed b y the WRSR instruction.
This bit works in conjunction with the the Write
Protect (WP) pin to control the hardware write protect
feature. Hardware write protection is enabled when
the WP pin is low and the WPEN bit is "1". Hardware
write protection is disabled when either the WP pin
is high or the WPEN bit is "0". When the hardware
write protection is on, only the writes to the
the non-volatile bits (WPEN, BP1, BP0) are disabled.
It is noted that the write enable latch must also
be set before the non-volatile bits can be progr ammed.

Bits[6:4] are "0" except when the status register is being

programmed. These bits are read-only.
BP[1:0] are the block write protect bits. These bits

specifies which blocks in the memory array are
write protected, as indicated in Table 3. These bits

are non-volatile and are programmed by the WRSR
instruction.

WEN indicates the status of the write enable latch. A "1"
means that the write enable latch is set. A "0" means

that the write enable latch is cleared. This bit
is read-only .

BSY indicates the status of the internal write cyle to the
memory array. A "1" means that the write cycle is in

progress. A "0" means the write cycle has finished
and the device is ready for the ne xt instruction.
This bit is read-only.

Ta b le 3 Bloc k "Write Protect" Assignment

---------------------------------------------------------------------------------------------

Status Register Fraction of Array Write Protected Memory Blocks
BP1 BP0 Write Protected 25C256

---------------------------------------------------------------------------------------------

0 0 0 None

---------------------------------------------------------------------------------------------

0 1 1/4 6000-

7FFF

---------------------------------------------------------------------------------------------

1 0 1/2 4000-

7FFF

---------------------------------------------------------------------------------------------

1 1 All 0000-

7FFF

---------------------------------------------------------------------------------------------

3

The contents of the status register can be read by the RDSR
instruction. The write protect enable bit, the b loc k write
protect bit, the write enable status, and the busy status of
the Turbo IC 25C256 can be found through RDSR. Three bits
of the status register can be altered by the WRSR instruction. The
write protect enable bit can be set to enable the hardware write
protect, and the block write protect bits can be set to control
the number of blocks to be write protected, according to Table 3.
When the status register is being programmed, the RDSR instruction
can be used to check the status of the BSY bit. All the other bits
will read back ones.

V ALID DAT A AT SI

The selected Turbo IC 25C256 senses the data on the SI pin
at the rising edge of SCK clock.

READ OPERA TION

The data in the memory array of the Turbo IC 25C256 can be
read as follows: The master pulls the CS pin of the
Turbo IC 25C256 low , and issues a READ instruction
to the SI pin, which is loaded into the instruction register.
The two address bytes of the memory location to be read are sent
next, which are loaded into the address counter . The two
most significant bits of the address are don't cares. The
data byte in the memory is shifted out onto the SO pin on the
falling edge of SCK. After the data b yte is shifted out, the address
counter is incremented by one. The next data byte is shifted
out. The sequential read continues for as long as the master
provides the clock and keeps CS lo w. When the address
counter reaches the highest address, it rolls over to the z ero
address (0). The read is terminated by bringing CS high.

WRITE OPERA TION

The write data can be written into the memory array of the
selected Turbo IC 25C256 as follows: The master pulls the CS pin
of the selected Turbo IC 25C256 low, and issues a WREN
instruction to the SI pin, which is loaded into the instruction
register. Then the master brings CS high to set the WREN latch. The master
pulls the CS pin low , and issues the WRITE instruction to the SI
pin, which is loaded into the instruction register. The two address
bytes of the memory location to be written are sent next, which
are loaded into the address counter. The first most significant bits
of the address is a don't care. The data byte to be written is
sent next. The data byte is stored in a data byte latch.
The address counter is incremented by one after the
data byte is shifted in. Up to 64 data bytes can be sent before
a write cycle is necessary. To start the internal write cycle, the
CS must be brought high after the least significant bit (D0)
of the last data byte has been loaded. If CS is brought high
at any other time, the write cycle will not start.

25C256

Turbo IC, Inc.

4

PRELIMINARY INFORMATION

25C256

Turbo IC, Inc.

To check whether the write programming has finished, the
master pulls CS low , and issues the RDSR instruction. The contents
of the status register is shifted out onto the SO pin. The BSY
bit can be checked. If BSY is "1", the write programming is still
in progress. If BSY is "0", the write programming has finished.
At the end of the write cycle, the WREN latch is automatically
reset.

INQUIRY
Please Contact :

Turbo IC, Inc., U.S.A.
Phone : [phone]
Fax : [phone]

5

PRELIMINARY INFORMATION

25C256

Turbo IC, Inc.

6

Timing Diagrams for Mode 1 (0,0)

PRELIMINARY INFORMATION

Synchronous Data Timing

CS

SCK

SI

SO

HIGH Z

V

IH

V

IL

IH

IH

IH

IL

IL

IL

V
V

V

V

V

V

HIGH Z

VALID IN

t

t

t

t

t

t

t

tt

t

CSS

WH

CSH

CS

WLH

SU

V

HO DIS

WREN Timing

CS

SCK

SI

SO

HI - Z

WREN OP CODE

WRDI Timing

CS

SCK

SI

SO

HI - Z

WRDI OP CODE

25C256

Turbo IC, Inc.

7

PRELIMINARY INFORMATION

RDSR Timing

CS

SCK

SI

SO

INSTRUCTION

HIGH IMPEDANCE

0

12

34567

8910

11 12 13 14

7

6

5

432

10

DATA OUT

WRSR Timing

CS

SCK

SI

SO

HIGH IMPEDANCE

INSTRUCTION

DATA IN

0123

45678

9

10 11 12

13 14

15

76

54

3

2

10

READ Timing

CS

SCK

SI

SO

HIGH IMPEDANCE

INSTRUCTION

BYTE ADDRESS

DATA OUT

0

12

345

6

78910 11 20 21 22 23

24

25 26 27 28 29 30

15 14 13 3 2

1

0

76543210

25C256

Turbo IC, Inc.

8

PRELIMINARY INFORMATION

WRITE Timing

CS

SCK

SI

SO

INSTRUCTION

BYTE ADDRESS

DATA IN

0

1

2

3

4567

89101120

21

22 23 24 25 26 27

28 29

30 31

15

14

13

3

2

1

07

654 321

0

HOLD Timing

CS

SCK

HOLD

SO

tt

t

tt

t

HD

CD

HD

CD

LZ

HZ

25C256

PRELIMINARY INFORMATION

Turbo IC, Inc.

D.C. CHARA CTERISTICS

Symbol Parameter Condition Min Max Units

Icc1 Active Vcc Current VCC = 2.7 V at 2 Mhz 3.0 mA

SO= Open

Icc2 Active Vcc Current VCC = 5.0 V at 5 Mhz 5.0 mA

S0= Open

Isb1 Standby Current Vcc = 2.7 v 0.5 uA

Isb2 Standby Current

Vcc = 5.5 v 2.0 uA

Iil Input Leakage Current Vin=Vcc Max 3 uA

Iol Output Leakage Current 3 uA
Vil Input Low V oltage -0.5 Vccx0.2 V
Vih Input High Voltage Vccx0.7 Vcc+0.5 V

V o l2 Output Low Vcc=4.5v Iol=3.0 mA 0.4 V

V o l1 Output Low Vcc=2.7v Iol=1.5 mA 0.3 V
V oh 2 Output High Vcc=4.5v Ioh=-1.6mA Vcc-0.8 V
V oh 1 Output High Vcc=2.7v Iolh=-100uA Vcc-0.8 V

* “Absolute Maximum Ratings” may cause per manent damage to the de-

vice. This is a stress rating only and functional operation of the device at
these or any other conditions above those indicated in the operation sec­tion of this specification is not implied. Exposure to absolute maximum
rating conditions for extended periods may affect device reliability.

ABSOLUTE MANXIMUM RATINGS
TEMPERATURE

Storage: -65° C to 150° C
Under Bias: -55° C to 125° C

ALL INPUT OR OUTPUT VOLTAGES

with respect to Vss +6 V to -0.3 V

RECOMMENDED OPERATING CONDITIONS
Temperature Range: Commercial: 0° C to 70° C

Industrial: -40° C to 85° C
Military: -55° C to 125° C

Vcc Supply Voltage: 2.7 to 5.5 Volts

4.5 to 5.5 Volts

Endurance: 1,000,000 Cycles/Byte
Data Retention: 100 Y ears

9

A.C. CHARA CTERISTICS

Symbol Parameter 2.7 volt 5.5 volt

Min Max Min Max Units
fSCK SCL Clock F requency 2.1 5.0 MHz
TRi Input Rise Time 2 2 us
tF1 Input Fall Time 2 2 us
tWH SCK High Time 200 80 ns
tWL SCK Low Time 200 80 ns
tCS CS High Time 250 100 ns
tCSS CS Setup Time 250 100 ns
tCSH CS Hold Time 250 100 ns
tSU Data-in Setup Time 50 30 ns
tH Data-in Hold Time 50 30 ns
tHD Hold Setup Time 100 40 ns
tCD Hold Hold Time 100 40 ns
tV Output Valid 200 80 ns
tHO Output Hold Time ns
tLZ Hold to Output Low Z 100 50 ns
tHZ Hold to Output High Z 100 50 ns
tDIS Output Disable Time 250 100 ns
tWC Write Cycle Time 10 10 ms

25C256

Turbo IC, Inc. 2153 O'Toole Ave., Suite G, San Jose, CA 95131 Phone: [phone] Fax: [phone]

See us at www.turbo-ic.com

Rev. 2.1 - 02/06/98

TURBO IC PRODUCTS AND DOCUMENTS

1. All documents are subject to change without notice. Please contact Turbo IC for the latest
revision of documents.

2. Turbo IC does not assume any responsibility f or any damage to the user that ma y result from
accidents or operation under abnormal conditions.

3. Turbo IC does not assume any responsibility for the use of any circuitry other than what
embodied in a Turbo IC product. No other circuits, patents, licenses are implied.

4. Turbo IC products are not authorized for use in lif e support systems or other critical systems
where component failure may endanger life. System designers should design with error
detection and correction, redundancy and backup features.

Turbo IC, Inc.

Part Numbers & Order Inf ormation

TU25C256PC-2.7

Operating Voltage
blank 4.5 to 5.5 V

-2.7 2.7 to 5.5 V

Temperature
C -Commercial
I -Industrial

Package

P -PDIP

S -SOIC

32K X 8

Serial
EEPROM

A.C. TEST CONDITIONS
Output Load : 1 TTL Load and Cl=100 pF

10

PRELIMINARY INFORMATION