Datasheet CMX228S1 Datasheet (MX COM Inc)

CMX228

COMMUNICATION ICs

DATA BULLETIN

ISDN Data and Telephony
Protocol Engine with x.25

Advance Information

Features Applications

•

Supports ITU Specifications

•

Supports Incoming and Outgoing Calls

•

Auto-bauding and Auto-parity

•

Hayes Compatible 'AT' Command Set

•

V.120 Rate Adaption

•

PPP Async to Sync Conversion

•

Supports CTR3 Approval

•

User Data and X.25 via B and D Channels

Full API Available

•

1

S/T Interface

CMX228

Parallel BUS

AM79C30

S/T BUS

Controller

+ Codec

IOM2 BUS

CLI / CIDCW + SPM

DTMF Rx

Dual FIFO

HDLC Driver

PSB-21525

CMX605

•

Feature Phones with Data Interfaces

•

Pay-Phones

•

PABX Telephones + Data

•

Data Terminal Adapters

•

EPOS Terminals

•

Remote Metering and Alarm Systems

•

H.320 Video Phones

Reference Designs Available

•

A

S
L

POTS 1

I

C

B

RS232

Interface

Driver

RS232

The CMX228 is an ISDN data and telephony protocol engine which implements the lower level ISDN interface
and communicates with the CMX605 and other standard devices to form a fully integrated ISDN chipset for
both voice and data communications. The CMX228 puts all the main data processing elements in a single
device. No ISDN software has to be written and simple ‘Plug and Play’ design results. This reduces
development time and provides a highly cost-effective hardware solution. By using proven circuit designs, the
designer can move quickly from initial concept through design in to manufacture.

The CMX228 supports one voice port over the ISDN Line, which can be used to provide ISDN telephony
services or a POTS line interface, and a single data channel, capable of operation at 115,200bps. The
CMX228 features a full set of ‘Hayes’ compatible AT command codes on its asynchronous data interface, in
addition to providing keypad-configurable voice telephony services. The CMX228’s feature set and
architecture allow most analog systems to be converted to an ISDN equivalent with enhanced features.

The CMX228 is designed to work with the AMD 79C30 S/T bus interface, the Siemens PSB-21525 HDLC
formatter and the MX-COM CMX605 POTS interface circuit, and also comes complete with embedded
applications software. In addition, the CMX228 offers data transfer (up to 16kb/s) over the D-channel by
using the X.25 protocol. To support the CMX228, MX-COM can also provide licensed reference designs on
user request. A flexible Applications Program Interface (API) allows users to customize the features and
operation of their own design. The CMX228 is available in an 80-pin QFP (CMX228S1) package.

1

The CMX228 is a data processor integrated circuit that supports the protocol layers 1, 2 and 3 of the ISDN protocol stack in accordance
with the specifications of CCITT (now ITU). These specifications, which are widely used around the world, might not be supported withi n
the U.S.

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CONTENTS

Section Page

1. Block Diagram................................................................................................................4

2. Signal List.......................................................................................................................5

3. External Components....................................................................................................7

4. General Description.......................................................................................................8

4.1 Glossary .............................................................................................................................. 9

4.2 Initialization........................................................................................................................ 10

4.3 ISDN Interface................................................................................................................... 10

4.3.1 Activation..............................................................................................................................10

4.3.2 De-activation or Line Disconnection.....................................................................................10

4.3.3 Line Failure Detection ..........................................................................................................10

4.3.4 Incoming Calls......................................................................................................................10

4.3.5 Multiple Subscriber Numbering............................................................................................11

4.3.6 Channel Mapping.................................................................................................................11

4.4 POTS Configuration .......................................................................................................... 12

4.4.1 Configuration and Control via DTMF Keypad.......................................................................12

4.5 POTS Operation................................................................................................................ 13

4.5.1 Keypad Operation ................................................................................................................13

4.5.2 Incoming POTS Calls...........................................................................................................13

4.5.3 Outgoing POTS Calls...........................................................................................................14

4.5.4 Connected Calls...................................................................................................................14

4.5.5 Call Clearing.........................................................................................................................14

4.6 Data Configuration............................................................................................................. 15

4.6.1 Hayes Command Set ...........................................................................................................15

4.6.2 Hayes Register Set ..............................................................................................................19

4.7 Data Operation..................................................................................................................24

4.7.1 Incoming B-Channel Data Calls...........................................................................................24

4.7.2 Outgoing B-Channel Data Calls...........................................................................................24

4.7.3 X.25 Data Calls on the D-Channel.......................................................................................24

4.7.4 Connected Calls...................................................................................................................24

4.7.5 Call Clearing.........................................................................................................................24

4.8 Application Programmer's Interface................................................................................... 24

4.9 Hardware Description........................................................................................................ 25

4.9.1 LED Status Indicators (LED1 to LED9, and ILFI).................................................................25

5. Application Notes ........................................................................................................26

5.1 General.............................................................................................................................. 26

5.2 Approvals........................................................................................................................... 26

MX-COM, Inc 2000 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC, 27105-1201, USA Doc. # 20480216.001
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6. Performance Specification..........................................................................................27

6.1 Electrical Performance ...................................................................................................... 27

6.1.1 Absolute Maximum Ratings..................................................................................................27

6.1.2 Operating Limits...................................................................................................................27

6.1.3 Operating Characteristics.....................................................................................................28

6.2 Packaging.......................................................................................................................... 33

MX-COM Inc. reserves the right to change specifications at any time and without notice.

MX-COM, Inc 2000 MX-COM, Inc.
4800 Bethania Station Road, Winston-Salem, NC, 27105-1201, USA Doc. # 20480216.001
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1. Block Diagram

Serial

Data Port

LED Status

Indicators

System Memory

and NVRAM

Hayes AT

Command

Handler

Task Scheduler,

Memory Manager,

Timers and Task Mailing

ISDN

B-channel

Data

Protocol

Stacks

HDLC

Chip

SLIC

CMX605

DTMF Detector

and

Caller Display

LED Status

Indicators

POTS Port

Handler

Figure 1: Block Diagram

ISDN

D-channel

Protocol

Stacks

LED Status

Indicator

ISDN

Interface

Chip

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2. Signal List

S1 Package Signal

Pin No. Name Type

1 SCL output EEPROM - Serial Clock
2 SDA bi-directional EEPROM - Serial Data
3 ISDNRST output ISDN S-interface Chip Reset
4 RI1 output RS232 Port1 Ring Indicator (high when inactive)
5 DCD1 output RS232 Port1 Data Carrier Detect (high when inactive)
6 CTS1 output RS232 Port1 Clear To Send (high when inactive)
7

8

RST

DV

DD1

input CMX228 Chip Reset (active low)

power

The digital positive supply rail. Levels and voltages are
dependent upon this supply. This pin should be decoupled to
DV

by a capacitor

SS

9

XTAL

output The output of the on-chip Xtal oscillator inverter

10 XTAL input The input to the oscillator inverter from the Xtal circuit

DV

11

SS1

power The digital negative supply rail (ground)

12 LED1 output POTS Port Off-Hook Indicator (HK1)
13 LED2 output RS232 Port 1 Auto-Answer Indicator (AA)
14 LED3 output RS232 Port 1 Data Carrier Detect Indicator (DCD)
15 LED4 output RS232 Port 1 Ready To Send Indicator (RTS)
16 LED5 output RS232 Port 1 Receive Data Indicator (RXD)
17 LED6 output RS232 Port 1 Transmit Data Indicator (TXD)
18 LED7 output RS232 Port 1 Data Terminal Ready Indicator (DTR)
19 LED8 output ISDN Line Activated Indicator (AR)
20

ST

output Watchdog Timer Stimulus

21 LED9 output POTS Port Call Connected Indicator (CN1)
22

23

WR

RD

output Memory Write Access Strobe
output Memory Read Access Strobe

24 A19 output Memory and Peripheral Address Bus
25 A18 output Memory and Peripheral Address Bus
26 A17 output Memory and Peripheral Address Bus
27 A16 output Memory and Peripheral Address Bus
28 A15 output Memory and Peripheral Address Bus
29 A14 output Memory and Peripheral Address Bus
30 A13 output Memory and Peripheral Address Bus
31 A12 output Memory and Peripheral Address Bus
32 A11 output Memory and Peripheral Address Bus
33 A10 output Memory and Peripheral Address Bus
34 A9 output Memory and Peripheral Address Bus
35 A8 output Memory and Peripheral Address Bus
36 A/D7 bi-directional Memory and Peripheral Address and Data Bus
37 A/D6 bi-directional Memory and Peripheral Address and Data Bus
38 A/D5 bi-directional Memory and Peripheral Address and Data Bus
39 A/D4 bi-directional Memory and Peripheral Address and Data Bus

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Description

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S1 Package Signal

Description

Pin No. Name Type

40 A/D3 bi-directional Memory and Peripheral Address and Data Bus
41 A/D2 bi-directional Memory and Peripheral Address and Data Bus
42 A/D1 bi-directional Memory and Peripheral Address and Data Bus
43 A/D0 bi-directional Memory and Peripheral Address and Data Bus
44 ASTB output Address/Data Bus Strobe (data bus selected if low)

DV

45
46 ~ input

SS0

power The digital negative supply rail (ground)

For manufacturer's use only. Connect to DV

directly

SS

47 PSBRES output HDLC Chip Reset
48 N/C output Do not make any connection to this pin
49 N/C output Do not make any connection to this pin
50 API-RXD input API/RS232 Port 2 Rx Data (inactive = high)
51 API-TXD output API/RS232 Port 2 Tx Data (high when inactive)
52 N/C output Do not make any connection to this pin
53 NC output Do not make any connection to this pin
54 ILFI output ISDN Line Failure Indicator

DV

55

DD0

power

The digital positive supply rail. Levels and voltages are
dependent upon this supply. This pin should be decoupled to
DV

by a capacitor

SS

56 RING1 output POTS Port Ringing Generator (low when not ringing)
57

1RING

58 CLIP1 output

output POTS Port Ringing Generator (high when not ringing)

POTS Port Line Voltage Adjustment (low when sending FSK to a
Caller Display unit. If low, it makes the SLIC present a high

impedance to the POTS line)
59 ILINE1 input POTS Port Hook Switch Status Detector (on-hook = low)
60

∼

input

For manufacturer’s use only. Connect to DV

directly

SS

61 REPLY input CMX605 C-BUS Interface - Reply Data
62

CMD-

output CMX605 C-BUS Interface - Command Data

DATA

63 SER-CLK output CMX605 C-BUS Interface - Serial Clock

AV

64

DD

power

The positive analog supply rail. Levels and voltages are

dependent upon this supply. This pin should be decoupled to

AV

by a capacitor

SS

65
66
67

AV

AV

REF1

SS

1CS

power
power The negative analog supply rail (ground)

A/D Reference Voltage. Connect to AVDD directly

output CMX605 C-BUS Interface (chip select for POTS Port)

68 N/C output Do not make any connection to this pin
69

70

AV
AV

71 NMI input

REF2
REF3

power
power

D/A Reference Voltage. Connect to AVDD directly

D/A Reference Voltage. Connect to AVSS directly

For manufacturer's use only. Connect to DV

directly

SS

72 API-INT input API Interrupt (inactive = high)
73

IRQ

input CMX605 C-BUS Interface - Interrupt (inactive = high)

74 PSBINT input HDLC Chip Interrupt
75 RXD1 input RS232 Port 1 Received Data - used for autobauding

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S1 Package Signal

Description

Pin No. Name Type

76 RTS1 input RS232 Port 1 Ready To Send (inactive = high)
77 ISDNINT input ISDN S-interface Chip Interrupt
78 DTR1 input RS232 Port 1 Data Terminal Ready (inactive = high)
79 RXD1 input RS232 Port 1 Received Data (inactive = high)
80 TXD1 output RS232 Port 1 Transmitted Data (high when inactive)

Table 1: Signal List

3. External Components

V

DD

SCL

SDA

ISDNRST

RI1
DCD1
CTS1

RST

DV

DD1

XTAL
XTAL

DV

SS1

LED1
LED2
LED3
LED4
LED5
LED6
LED7
LED8

N/C

CS1

V

DD

SS

REF1

DD

AV

AV

AV

REPLY

SER-CLK

CMD-DATA

(V )

SS

ILINE1
CLIP1
RING1
RING1
DV
ILFI
N/C
N/C
API-TXD

API-RXD
N/C
N/C
PSBRES
(V )
DV
ASTB
A/D0
A/D1
A/D2

SS

DD0

SS0

V

DD

V

DD

RXD1

REF2

REF3

AV

TXD1

RXD1

DTR1

RTS1

ISDNINT

RXD1

PSBINT

IRQ

API-INT

NMI

AV

CMX228S1

ST

RD

WR

LED9

A19

A18

A17

A16

A15

A14

A13

Figure 2: CMX228 Pin-Out

The CMX228 is to be used as part of a chip-set. Please refer to Section 5 for details of the

Note:

A12

A11

A10

A9

A/D7

A/D6

A/D5

A/D4

A/D3

V

SS

A8

recommended chip-set.

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4. General Description

The CMX228 is a single-chip data processor which has been mask programmed with firmware to implement
an ISDN protocol stack. This enables the CMX228 to interface an analog (POTS) port and a digital (RS232)
port to an ISDN S-bus network connection. Key variables are stored in an external EEPROM and the user
can provide additional features by adding external ROM and RAM. Access to the firmware Application
Programmer's Interface (API) facilitates the seamless integration of the user's additional features with the pre­programmed ISDN to POTS and RS232 interfaces.

The CMX228 is intended for use as part of an ISDN chipset and all descriptions in this data sheet refer to this
implementation, which is shown in Figure 3. The use of alternative chipsets is not supported.

The firmware supports connection to an ISDN S-bus
controller and the AMD AM79C30 ST controller with integral PCM codec for a single POTS port.

The CMX228 interfaces with a CMX605 Tone Generator and DTMF Receiver chip, which decodes incoming
DTMF tones and generates certain call progress signals (e.g. busy tone) normally originating from an analog
telephone exchange. The firmware translates the CMX605 data into ISDN D-channel commands and vice
versa to support both incoming and outgoing calls. For the ISDN interface, D-channel commands sufficient
for standard telephony applications are implemented. With the aid of a small amount of discrete circuitry,
exchange battery voltage, ringing current, line reversal and off-hook detection are also supported, to complete
the POTS interface.

The CMX228 also provides a data port that can drive a standard RS232 interface with the aid of a Maxim
MAX238, or similar, level converter. The firmware provides support for incoming and outgoing data calls,
RS232 auto-bauding from 9600bps to 115200bps, auto parity detection, RTS/CTS flow control, call clearing
on loss of DTR, V.120 rate adaption, PPP async to sync conversion, X.25 protocol on both B and D-channels,
packet assembly and disassembly for X.25, and a comprehensive set of Hayes commands (which facilitate
the use of normal PC-based modem software). The CMX228 has dedicated outputs for visible indicators
(LEDs), which can be used to provide information on the call status. Support for Multiple Subscriber
Numbering is also included in the firmware.

The CMX228 can be configured either by means of keypad (DTMF) programming via the POTS port or by
means of an extended Hayes command set via the RS232 port. Configuration parameters allow the user to
change (for example) the format and cadence of the ringing signal, so as to facilitate use of the CMX228 in
different countries. Each POTS and RS232 interface is able to configure the variables relevant to its own use.

An Application Programmer's Interface (API) is available and is described separately in Section 4.8. Further
details are available on completion of a Non-Disclosure Agreement. Please contact MX-COM directly for
further details.

The firmware and finite state machine embedded in the CMX228 have been used in products that have
gained ETSI CTR3 approval.

network interface via the Siemens PSB21525 HDLC

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4.1 Glossary

ACCM
API
CIDCW
CLI
CRC
CTS
DCD
DDI
DTE
DTMF
DTR
HDLC
IA5
IE
ILFI
ISDN
LAPB
LAPD
LCGN
LED
LLI
MFO
MSN
NUA
NUI
PAD
PC
PCM
POTS
PPP
PVC
RI
RNR
RR
RTS
SABM
SABME
SLIC
SPM
SVC
TEI

Asynchronous Control Character Map
Application Programmer’s Interface
Caller Identification During Call Waiting
Calling Line Identification
Cyclic Redundancy Check
Clear to Send
Data Carrier Detect
Direct Dialing Inwards
Data Terminal Equipment
Dual Tone Multiple Frequency
Data Terminal Ready
High Level Data Link Control
International Alphabet No 5
Information Element
ISDN Line Failure Indicator
Integrated Services Digital Network
Link Access Procedure - Balanced
Link Access Procedure on the D-Channel
Logical Channel Group Number
Light Emitting Diode
Logical Link Identifier
Multiple Frame Operation
Multiple Subscriber Numbering
Network User Address
Network User Identification
Packet Assembler/Disassembler
Personal Computer
Pulse Code Modulation
Plain Old (Analog) Telephone Service
Point to Point Protocol
Permanent Virtual Circuit
Ring Indication
Receiver Not Ready
Receiver Ready
Ready to Send
Set Asynchronous Balanced Mode
Set Asynchronous Balanced Mode Extended
Subscriber Line Interface Circuit
Subscriber Pulse Metering
Switched Virtual Circuit
Terminal Endpoint Identifier

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4.2 Initialization

On power-up, the CMX228 assumes its default values, which are factory programmed into the firmware. It
then performs a self-test, during which all of the LED pins and the ILFI pin are held high for 3s. If the test is
unsuccessful, the CMX228 remains in this condition.

If the test is successful, the CMX228 reads its preset values from the attached EEPROM and examines the
state of the ISDN link (i.e. Layer 1) before commencing normal operation. On power-up, the ISDN link is de­activated, the POTS port is assumed to be on-hook, ringing is disabled and the RS232 port is in the Hayes
command state.

4.3 ISDN Interface

Simultaneous voice and data calls are possible but only one of each type. If a call is active (e.g. ringing,
connected or clearing down) and an incoming call of the same type (data or voice) is received, that call will be
rejected with user busy as the cause. Incoming calls are firstly checked for other calls present, then the MSN
is checked for validity, then the channel mapping, so that responses will be handled accordingly.

When channel mapping is enabled, outgoing calls will request the channel enabled. When not enabled, a
request for any channel is made. If no free channels are available for outgoing calls, a locally generated busy
tone is returned to the analog port or the appropriate Data Call Result Code is returned to the digital port.

4.3.1 Activation

Activation occurs in the following circumstances:

•

The ISDN network activates.

•

The device connected to the analog port goes off hook.

•

The device connected to the data port sends a Hayes dial command.

The Terminal Endpoint Identifier (TEI) is either negotiated (Hayes register !C7 = 64) or fixed
(Hayes register !C7 = 0 to 63). Line powering of the CMX228 is not supported.

The 'AR' indicator (LED8) toggles between high and low states when the CMX228 is powered up, and
remains constantly low once the CMX228 identifies an activated ISDN line.

ISDN line power detection is not implemented and the CMX228 will negotiate a new TEI on any new network
activation.

4.3.2 De-activation or Line Disconnection

De-activation or line disconnection causes the TEI to be removed. Upon re-connection the CMX228 will only
be re-activated and request a new TEI when one of the conditions in the above section is met.

4.3.3 Line Failure Detection

If the line failure detection parameter is enabled (either via the POTS port or via the RS232 interface) the
CMX228 will check that Layer 2 communications are active every sample period of 30 seconds. If Layer 2
communications are not active, the CMX228 will attempt to activate them. If they remain inactive for 2 sample

periods, the line is deemed to have failed, so then the ILFI pin is set high and both RING1 and

pins

1RING

are set low. The CMX228 continues to attempt to activate the line and if it becomes active and stays active
for 2 sample periods, then the ILFI pin is set low and RING1 and

pins are restored to their default

1RING

settings.

4.3.4 Incoming Calls

Incoming voice calls and calls from analog lines are directed to the analog port and all other incoming calls
are directed to the RS232 port.

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4.3.5 Multiple Subscriber Numbering

Multiple Subscriber Numbering (MSN) enables each POTS or RS232 port of the CMX228 to have its own
telephone number. Up to 23 digits can be saved as the MSN for each port.

All incoming SETUP messages will be checked for the presence of a Called Party Number Information
Element (IE). If one is present it is compared with the saved MSN number (if present), starting with the last
digit of both numbers. Comparison continues until there are no more numbers in the MSN saved number or
the incoming Called Party Number or there is a difference between the numbers. The MSN is said to match if
the saved MSN and the incoming calls’ Called Party Number are the same for the duration of the shorter
number (i.e. if the digit ‘1’ is saved and the received Called Party Number is 654321, then the MSN matches).
If there is no saved MSN, the Called Party Number is ignored and call processing continues.

When there is a saved MSN and the Calling Party Number transmit is enabled, all outgoing call SETUP
messages will contain a Calling Party Number Information Element.

Notes:

1. When a CMX228 with MSN saved and Calling Party Number transmit enabled is connected to some
exchanges, no dial tone is heard when going off-hook.

2. Disabling the Calling Party Number transmit will mean that the called party may not receive the Calling
Line Identification (CLI), or if they do receive a CLI it will probably be the base number and not the
number specific to the calling telephone.

4.3.6 Channel Mapping

It is possible to configure the CMX228 so that analog and/or digital ports will only originate calls to and
respond to calls from a specific ISDN B-channel. This is a useful feature if, for example, you wish to have a
Hunt Group on your ISDN line and only want one voice or data port to ring on an incoming call.

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4.4 POTS Configuration

4.4.1 Configuration and Control via DTMF Keypad

Configuration can be carried out at any time by causing the POTS port to go off-hook and then immediately
entering a configuration sequence of DTMF tones. The sequence signaled to the CMX228 will determine the
configuration to be performed, as shown in the following table.

Configuration

Sequence

$02$

$90$

$90$

$93$

$93$

$94$

$94$

$95$

$95$

$96$

$96$

$97$

$97$

$9$$

1234567890#

Once the ‘

#

#

n#

#

n#

#

n#

#

1#

#

1#

#

1#

$’ has been recognized, each digit pressed is then checked for validity as a configuration

Test watchdog

Clear MSN Clears any saved digits N/A
Save Multiple Subscriber

Number (MSN)
Clear country code Country code is set to UK by default N/A

Change country code

Clear channel mapping

Enable channel mapping Where n = 1 or 2 for the appropriate channel.
Disable Calling Party No.

transmit
Enable Calling Party No.

transmit

Disable DDI transmit

Enable DDI transmit

Disable line failure detection

Enable line failure detection

Initialize all configurations.

sequence. If any digit pressed is not a valid configuration digit, all digits pressed so far will be transmitted to
the network in INFORMATION messages as Keypad Information Elements, until a ‘#’ is entered (with the
exception of ‘$

#’ being entered, see Keypad Operation below). If the first four digits received are a valid
configuration sequence then the configuration mode is entered. When a valid configuration has been
completed the CMX228 will send a single DTMF tone to the POTS port. If a valid configuration sequence is
received but subsequent digits are invalid, then subsequent digits entered will be ignored and two DTMF
tones will be sent to the POTS port.

If the port goes on-hook part way through configuration, it will cause any digits received so far to be ignored.
Configurations can be performed consecutively with the exception of the test function (where the attached
handset must be replaced immediately after the configuration has been audibly signaled to the POTS port).
All configurations entered will be retained after a power-down as they are stored in the external EEPROM.

Name Description Default

Puts the CMX228 into a permanent loop, not
updating the external watchdog counter, so after
2s it should reset.

n = MSN (up to 23 digits) Clear

n = country code
0 = UK
1 = Belgium
2 = Rest of Europe

Incoming calls on any channel are accepted
(provided other parameters are valid e.g. MSN).

Outgoing call SETUP messages do not contain
any Calling Party Number Information Elements.

Outgoing call SETUP messages contain Calling
Party Number Information Element with number
set to saved MSN (if a number is present).

Prevents digits being transmitted to the POTS
port upon call connection.

Upon connection of a call on the POTS port, if
there was a Called Party Number Information
Element present in the incoming call setup
message, the digits are sent as DTMF tones to
the POTS port.

Once the CMX228 is de-activated it stays de­activated until the network re-activates it or an
outgoing call needs to be made.

The CMX228 checks to see if the ISDN line is
activated and Layer 2 communications can be
made. It then sets the ILFI pin accordingly.

Resets all of the configuration variables back to
their default values.

N/A

UK

N/A

No channel

map

N/A

Enabled

N/A

Disabled

N/A

Disabled

N/A

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4.5 POTS Operation

4.5.1 Keypad Operation

The CMX228 supports ISDN keypad messages for control of Network Supplementary services either before
or during call establishment. When dialing a number (i.e. off-hook and dial tone audible on POTS port), or if a
call has been disconnected by the network but the POTS port has not yet gone on-hook, any keypad string
entered will be sent to the network as ‘Keypad Information Elements’ within INFORMATION messages.
Keypad strings are defined as the following sequences of digits, with the exception of the configuration strings
defined in the previous section:

$...#

$

When a call is connected, pressing the recall key results in all subsequent key presses being sent to the
network as ‘Keypad Information Elements’ within INFORMATION messages, until the handset is replaced.
The tones generated by the key presses are also passed down the B-channel, so the remote user will be able
to hear them.

4.5.2 Incoming POTS Calls

An incoming POTS call is identified by the Bearer Capability Information Element of the SETUP message
being set to ‘Speech' or ‘3.1kHz Audio’. The call will be routed to the POTS port if it satisfies the following
three conditions:

When the call is routed to the port, the ringing signal for that port will be applied by means of the RING1 and

The call is answered when the port with ringing signal goes off-hook. The ringing signal is then stopped and
the ISDN call is connected to that port.

#...#

#...#

• The port is on-hook.

• The MSN saved for the port matches the Called Number in the incoming SETUP message, or no

MSN is specified for the port, or there is no Called Number in the SETUP message. See Section

4.3.5 for details of POTS port MSN selection.

• The ISDN B-channel on which the call is placed (as indicated in the SETUP message) is compatible
with the channel-mapping configuration for the port. See Section 4.3.6 for details of POTS port
channel mapping selection.

pins.

1RING

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4.5.3 Outgoing POTS Calls

Outgoing calls are initiated when the POTS port goes off-hook. An ISDN SETUP message is sent to the
network with the Bearer Capability Information Element set to 'Speech'. The dial tone presented by the
network on that ISDN B-channel which was selected by channel mapping (See Section 4.3.6), will be routed
to the POTS port.

When DTMF tones are received from the POTS port, they are sent to the network either as Called Party
Number or Keypad Information Elements. Keypad Information Elements are discussed in Section 4.5.1.

Receipt of a valid DTMF tone will prompt its conversion to IA5 coded digits, as shown in the following table
(IA5 hex digits are in brackets). If the first valid digit to be received is a ‘$’ then the configuration mode is
entered and subsequent digits will be monitored and saved as indicated in Section 4.4.1. If the first tone
received is not a ‘$’ or ‘#’ (See Section 4.5.1) that digit and all subsequent digits will be passed to the network
in an INFORMATION message as a Called Party Number Information Element. Digits received before the
network has returned the SETUP ACK message are saved. Upon receipt of the SETUP ACK any saved
digits will be transmitted.

The DTMF tone mapping is as shown below:

Low Group

High Group (Hz)

(Hz) 1209 1336 1477 1633

697 1 (31) 2 (32) 3 (33) A (not used)
770 4 (34) 5 (35) 6 (36) B (not used)
852 7 (37) 8 (38) 9 (39) C (not used)
941

(2A) 0 (30)

$

#

(23)

D (not used)

Once the network has indicated that the full number has been received, no further digits will be sent to the
network. All tones and announcements from the network (e.g. ringing, NU, busy etc) and audio (if the call is
connected) will be routed to the POTS port, until that port goes on-hook.

4.5.4 Connected Calls

Once a call is connected to the analog port, whether it was incoming or outgoing, a LED indicator pin is set
high to indicate that the call is connected. See Section 4.9.1 for details of the LED indicator pins. Once the
call is disconnected, either by receipt of a DISCONNECT message from the network or an on-hook indication,
that LED indicator pin is set low.

During a call, if a Recall (i.e. a line break of appropriate length) is received from the POTS port, the CMX228
will start to look for DTMF tones received on the POTS port. Any tones received will then be sent to the
network in ISDN INFORMATION messages, as Keypad Information Elements

.

4.5.5 Call Clearing

The call is cleared either by the port going on-hook or by the ISDN network.

The ISDN B-channel that was being used is not released until the POTS port has gone on-hook.

Note:

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4.6 Data Configuration

4.6.1 Hayes Command Set

The following Hayes commands are supported:

A - Answers a call
D - Dial
E - Echo Hayes commands or not
H - Hang-up
I3 - Firmware part number
Q - Result code display
V - Result code form
X - Result code set
&C - Carrier detect
&D - Data terminal ready
&F - Load factory default
&K - Flow control
&V - View active and stored profiles

Valid Hayes commands are responded to with an 'OK' result code. Invalid commands are rejected with an
'ERROR' result code.

If when entering an AT command, no command or register name suffix is supplied, a suffix of zero is
assumed. If when changing a register value, no value is supplied a value of zero or an empty string is
assumed: e.g. ATS0=<CR> is equivalent to ATS0=0<CR>.

If a data call is active when a command is entered, the command will be processed. The ATO command will
respond ‘OK’, but will not then enter the data state: it will stay in the command state.

Where commands set a parameter, these are saved in external EEPROM if they are entered correctly.
The CMX228 will auto-baud and auto-parity on Hayes commands at the following speeds:

•

9600bps

•

19200bps

•

38400bps

•

57600bps

•

115200bps

The auto-bauding process looks for the characters ‘AT’ or ‘at’ either as 8 bits no parity or 7 bits even, or odd,
parity. An error in the auto-bauding process results in auto-bauding being restarted.

After auto-bauding successfully, the CMX228 waits to receive a complete Hayes command line before
processing it. Embedded spaces are ignored and the case (upper or lower) of characters after the ‘AT’ does
not matter. The command line is terminated by <CR>, by 250 characters (not including the ‘AT’) or by a time­out (from successful auto-bauding on an ‘AT’) of 180 seconds.

All characters in the Hayes command, including the ‘AT’ and <CR> terminator are echoed (if E1 is set) by the
CMX228 as they are sent by the DTE.

Receipt of a backspace will cause the CMX228 to send a "back space, space, back space" sequence of
characters to the DTE to allow the terminal to clear its screen of the last character. Also the last character
received will be discarded unless the last characters received were the ‘AT’ used for auto-bauding, i.e. the
‘AT’ is never deleted.

The escape sequence ‘+++’ (with Guard Time = 1s before and after the sequence) will cause the CMX228 to
enter the command state from the data state and to return an ‘OK’ response. Sending an ATO command will
be ignored, i.e. the CMX228 remains in the command state.

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Detailed descriptions of the Hayes Commands listed in Section 4.6.1:

A (Answer)

Format: ATA<CR>
Causes the CMX228 to answer an incoming data call, by sending a CONNECT message to the network. If

a CONNECT ACK is received the CMX228 enters the data state after returning a ‘CONNECT XXX’ result
code to the DTE on the RS232 port (where the XXX is the speed in baud). If a RELEASE, RELEASE
COMPLETE or DISCONNECT message is received a ‘NO CARRIER’ result code is returned. The
command is not valid if there is no incoming call and it will return ‘ERROR’.

D (Dial)

Format: ATD{DN}<CR>
Format: ATDT{DN}<CR>
Format: ATDP{DN}<CR>

{DN} is a directory number of up to 23 ASCII characters from 0..9, $ and #. This form of the ATD command
causes an outgoing SETUP message to be sent to the network with a Called Party Number Information
Element which contains the digits included in the command. Any commands that follow this command are
ignored.

If the CMX228 receives any character from the DTE after an ATD command, which causes a SETUP
message to be sent to the network, and before the call is connected, the attempt to make a call is abandoned,
i.e. a DISCONNECT message will be sent to the network and a ‘NO CARRIER’ result code returned.

Calls are established with the D command, irrespective of the state of the DTR pin. The result code response
is either:

'CONNECT' - call successful. The CMX228 will automatically enter the data state.
'NO CARRIER' - call rejected by the remote user or the network
'NO DIALTONE' - ISDN link down
'BUSY' - remote user busy and other causes

Calls are cleared in the following way:

i. The remote end or network clears the call by sending a DISCONNECT message or the ISDN line

fails/is removed: 'NO CARRIER' is sent to DTE.

ii. DTR is dropped (with a de-bounce period of 50ms) by DTE causing the CMX228 to send a

DISCONNECT message to the network and enter the disconnect state, awaiting a RELEASE
COMPLETE from the network. The CMX228 sends the 'OK' response when clearing of the ISDN call
is complete i.e. RELEASE and RELEASE COMPLETE messages have been transmitted across the
network, (dependant upon the state of &D command).

iii. The DTE issues the escape sequence ‘+++ ‘(with Guard Time = 1s before and after the sequence),

receives an 'OK' response and then issues the Hang-up command (see section on H command
below). The CMX228 sends the 'OK' response when clearing of the ISDN call is complete.

Incoming calls are indicated by a 'RING' result code. The call is automatically answered if S0 = 1 or more. If
S0 = 0 an ATA command must be entered, then a CONNECT message is sent to the network.

E (Echo)

Format: ATEn<CR>
Suffix n

Description
0 Echo off
1 (default) Echo on

This command tells the CMX228 whether or not to echo the characters received from the DTE when in
command mode. When echo is on, all non-control characters received from the DTE are echoed back to it.

H (Hang-up)

Format: ATH<CR>
Causes the CMX228 to clear the data call in progress. The command is not valid if there is no data call in

progress but always returns an ‘OK’ result code. It is only valid in the command state when a data call is in
operation, when it will send a DISCONNECT message to the network. Upon receipt of RELEASE, a
RELEASE COMPLETE is transmitted to the network and ‘OK’ returned to the DTE.

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I3 (Firmware Part Number)

Format: ATI3<CR>
Causes the CMX228 to return the part code and revision level to the DTE:

"CMX228: Vn.nn" where n.nn = version number

Q (Result Code Display)

Format: ATQn<CR>
Suffix n

Description
0 (default) Result codes enabled
1 Result codes suppressed
2 Result codes are suppressed when an incoming call is received,
otherwise enabled

V (Result Code Form)

Format: ATVn<CR>
Suffix n

Description
0 Result codes sent as numbers (see Data Call Result Codes below)
1 (default) Result codes sent as words. This instructs the CMX228 to send the
result codes as words or numbers to the DTE.

X (Result Code Set)

Format: ATXn<CR>
Suffix n

Description
0 0...4
1 0...4, 12, 14, 18, 28, 31
2 0...4, 12, 14, 18, 28, 31
3 (default) 0...4, 6, 7, 12, 14, 18, 28, 31
4 0...4, 6, 7, 12, 14, 18, 28, 31

This command causes the CMX228 to limit the data call result codes used to a given set. See Data Call
Result Codes below for a list of codes and their meanings.

Data Call Result Codes

The data call result codes supported are:
Numbers

Words
0 'OK'
1 'CONNECT'
2 'RING'
3 'NO CARRIER'
4 'ERROR'
6 'NO DIALTONE'
7 'BUSY'
12 'CONNECT 9600'
14 'CONNECT 19200'
18 'CONNECT 57600'
28 'CONNECT 38400'
31 'CONNECT 115200'

&C (Carrier Detect)

Format: AT&Cn<CR>
Changes the operation of the RS232 DCD (Data Carrier Detect) signal.
Suffix n

Description
0 Ignore connection status, keep DCD high and LED3 pin low (ie ON).
1 (default) DCD tracks the status of the data connection, raised when the call
is connected, lowered when cleared. LED3 pin tracks the inverse status
of the DCD pin (i.e. high when data connection is cleared).

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&D (Data Terminal Ready)

Format: AT&Dn<CR>
Determines the CMX228 operation if DTR is lowered during a call.
Suffix n

Description
0 No action
2 (default) B or D-channel data call is cleared and auto-answer is suspended until
DTR is raised again.

If &D2 is set and DTR is low when an incoming call is received, the call is accepted and Ring Indication is
sent to the DTE. If an incoming call has been accepted and &D2 is set when DTR is lowered, the call is
cleared.

&F (Load Factory Profile)

Format: AT&F<CR>
Sets the following commands and registers to their default values.

It does not change the %A !B, !C registers or the &Z command.

Commands: E Q V X &C &D &K

Registers: S0 S37 %B %D %E %L

Format: AT&F9<CR>
Sets all commands and registers to the default values and resets LED indicator and RS232 interface pins

accordingly.

&K (Flow Control)

Format: AT&Kn<CR>
Indicates the method of flow control to be used between the CMX228 and the DTE when in the data state.

There is no flow control when the CMX228 is in the command state.
Suffix n

Description
0 No flow control
3 (default) Bi-directional RTS/CTS signals
Flow control is only active when in an active data call, i.e. not when dealing with Hayes commands.
Flow control is applied to the DTE in the following situations:

i. The remote end signals flow control (the mechanism is protocol dependent).

ii. Several buffers of data are held waiting transmission across ISDN.

Flow control is applied to the remote end (the mechanism is protocol dependent) if excessive data is held
pending transmission to the DTE, so as to prevent local buffer overflow.

&V (View Active/Stored Profiles)

Format: AT&V<CR>
Causes the CMX228 to display the following command and register values for the stored profile:

Commands: E Q V X &C &D &K &Z

Registers: S0 S37 %A !C %E %B %D %L !B

&Z (Store Directory Number)

Format: AT&Z3={DN}<CR>
This command instructs the CMX228 to store a directory number. The stored directory number is then used

by the X.25 call setup as the ‘Calling NUA’.
A directory number consists of a string of characters from the set 0..9, $ and #. The ‘=‘ character can be

omitted. Where a store number is entered, only the value 3 will give an ‘OK’ response. The contents of the
&Z directory number are displayed by using the &V0 command. Up to 20 digits can be saved. The number
must be in quotes. e.g. at&z3 =’12345’.

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4.6.2 Hayes Register Set

In addition to the commands, there are a group of registers for which data is entered in the following format:
AT{register}={value}<CR>. The following Hayes registers are supported:

S0 - Number of rings on which to auto- answer
S37 - Maximum rate adaption speed
%A2 - B/D - channel protocol
%B0 - X.25 receive window size
%B1 - X.25 transmit window size
%B2 - X.25 receive packet size
%B3 - X.25 transmit packet size
%B13 - X.25 NUI
%B18 - X.25 user data
%D0 - X.25 default receive window size
%D1 - X.25 default transmit window size
%D2 - X.25 default receive packet size
%D3 - X.25 default transmit packet size
%D9 - X.25 group number
%D10 - X.25 channel number
%E8 - V.120 MFO mode selection
%L3 - PAD forwarding character
%L4 - PAD idle timer
%L10 - PAD line folding
!B1 - LAPB T1 timer
!B2 - LAPB T4 timer
!B3 - LAPB N2 retry count
!B5 - X.25 LAPB active/passive
!C4 - B1 - channel configuration
!C5 - B2 - channel configuration
!C6 - Multiple Subscriber Numbering
!C7 - TEI selection
!C8 - ISDN Line Failure Detection enable/disable

The following is a more detailed description of the Hayes registers listed above:

S0 (Rings on Which to Auto-answer a Data Call)

Range

Default Description

0 to 255 0 If set to 0 auto-answering will be disabled.
Any other value will cause one ‘RING’ result code to
be sent to the DTE after which the call is answered.

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S37 (Maximum Rate Adaption Speed)

This forces the baud rate when handling incoming calls, to that defined by the S37 register contents, provided
auto-answer is set. Once a call is terminated the baud rate remains that set by the S37 register.

Value

Rate (baud)
0 (default) Same as last AT speed
9 9600
12 19200
13 38400
18 57600
31 115200

%A2 (CSD Protocol)

Selects the protocol to be used for the circuit switched data calls. Note that %A2 cannot be changed while a
B or D-channel call is active.

Value

Description
2 (default) V.120 Rate Adaption on B-channel.

3 Voice Calls.
4 X.25 Rate Adaption on B-channel.
5 X.25 packet calls on D-channel.
6 X.25 to a packet switched data network reached by a B-channel data
call. This involves a two stage call set up. Firstly a circuit switched call
must be established to the X.25 node, followed by a virtual call to an X.25
destination. The ATD command is used for both call requests.
15 PPP.
20 Transparent protocol.

4.6.2.1 X.25 Virtual Circuit Parameters

All %B registers can be read using the %Bn? command.

%B0 (X.25 Receive Window Size)

Defines the maximum number of X.25 packets that may be received before an acknowledgement is sent.
Value

Description
0 (default) Use the default value appropriate to the type of call, without negotiation,

see %D registers.
1 to 7 Negotiate the receive window size according to the value entered.

%B1 (X.25 Transmit Window Size)

Defines the maximum number of X.25 packets that may be transmitted before an acknowledgement is
expected. Use of the default value is recommended.

Value

Description
0 (default) Use the default value appropriate to the type of call, without negotiation,

see %D registers.
1 to 7 Negotiate the transmit window size according to the value entered.

%B2 (X.25 Receive Packet Size)

Defines the maximum number of bytes that may be received in an X.25 packet.
Value

Description
0 (default) Use the default value appropriate to the type of call, without negotiation,

see %D registers.
7 Negotiate for a maximum 128 bytes per packet.
8 Negotiate for a maximum 256 bytes per packet.
9 Negotiate for a maximum 512 bytes per packet.
10 Negotiate for a maximum 1024 bytes per packet.

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%B3 (X.25 Transmit Packet Size)

Defines the maximum number of bytes that may be transmitted in an X.25 packet.
Value

Description
0 (default) Use the default value appropriate to the type of call, without negotiation,

see %D registers.
7 Negotiate for a maximum 128 bytes per packet.
8 Negotiate for a maximum 256 bytes per packet.
9 Negotiate for a maximum 512 bytes per packet.
10 Negotiate for a maximum 1024 bytes per packet.

%B13 (Network User Identification String)

A maximum of 32 ASCII characters. The default value is an empty string. The Network User Identification
(NUI) string is used to identify the terminal to the packet switched network if necessary. If there is at least one
character present, the NUI is transmitted to the network when the call is established.

%B18 (User Data)

Up to 12 ASCII characters. Default is an empty string. The X.25 user data field which is sent when the X.25
call is established.

4.6.2.2 X.25 Parameters

All %D registers can be viewed using the %Dn? command.

%D0 (Default receive Window Size (Negotiated))

Defines the default maximum number of X.25 packets that may be received before an acknowledgement is
sent, only in use if %B0=0.

Range

Default Description

1 to 7 2 Default receive window size.

%D1 (Default Transmit Window Size (Negotiated))

Defines the default maximum number of X.25 packets that may be transmitted before an acknowledgement is
expected, only in use if %B1=0.

Range

Default Description

1 to 7 2 Default transmit window size.

%D2 (Default Receive Packet Size (Negotiated))

Defines the default maximum number of bytes that may be received in an X.25 packet, only in use if %B2=0.
Value

Description
7 Maximum 128 bytes per packet.
8 (default) Maximum 256 bytes per packet.
9 Maximum 512 bytes per packet.
10 Maximum 1024 bytes per packet.

%D3 (Default Transmit Packet Size (Negotiated))

Defines the default maximum number of bytes that may be transmitted in an X.25 packet, only in use if
%B3=0.

Value

Description
7 Maximum 128 bytes per packet.
8 (default) Maximum 256 bytes per packet.
9 Maximum 512 bytes per packet.
10 Maximum 1024 bytes per packet.

%D9 (Group Number)

Defines the group number used in outgoing call setup messages.
Range

Default Description

0 to 7 4 Group number.

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%D10 (Channel Number)

Defines the channel number used in outgoing call setup messages.
Range

Default Description

0 to 255 0 Channel number.

4.6.2.3 V.120 Parameters
%E8 (Multiple Frame Operation Mode Selection)

In Multiple Frame Operation (MFO) mode, frames are acknowledged and retransmitted if errors occur.
Value

Description
0 MFO mode on.
1(default) MFO mode off.

4.6.2.4 X.25 PAD Parameters

All %L registers can be viewed using the %Ln? command.

%L3 (Selection of Data Forwarding Characters)

This register is used to specify the characters which, when received from the DTE, will cause the current
packet of data to be transmitted. If set to zero, the packet is not transmitted until either the idle timer (%L4)
expires, or the packet becomes full (%B3). The values listed below may be added together to combine the
character sets indicated. The characters are as described in the ASCII character set.

Value

Description
0 (default) None.
1 A to Z, a to z and 0 to 9.
2 CR.
4 ESC, BEL, ENQ and ACK.
8 DEL, CAN and DC2.
16 ETX and EOT.
32 HT, LF, VT and FF.
64 NUL, SYN, ETB, EM, SUB, FS, GS, RS, and US.

%L4 (Idle Timer)

Range

Default Description

0 to 40 0 Specifies the duration of the timer (in units of 1/20
second) that, when it expires, causes the contents of
the current packet to be forwarded. If set to zero, there
is no timed forwarding.

%L10 (Line Folding)

Range

Default Description

0 to 255 0 Specifies the line length required. When the specified
number of characters have been sent to the DTE a
carriage return and line feed are sent to ensure that lines
do not exceed the required length. A value of zero
disables line folding.

If %L3 and %L4 are both 0, characters will be forwarded as they become available.

Note:

4.6.2.5 B Channel LAPB Parameters

All !B registers can be viewed using the !Bn? command.

!B1 (LAPB T1 Timer)

Range

Default Description

1 to 255 3 Sets the value, in seconds, of the LAPB T1 timer.

!B2 (LAPB T3 Timer)

Range

Default Description

1 to 255 15 Sets the value, in seconds, of the LAPB T3 timer.

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!B3 (LAPB N2 Retry Count)

Range

Default Description

1 to 255 4 Sets the number of times the LAPB protocol will retry
sending before giving up and applying recovery
procedures.

!B5 (Active/Passive)

Value

Description
0 (default) X.25 is Active i.e. initiates link initialization.
1 X.25 is Passive and waits for the network to initialize the link.

4.6.2.6 Basic Configuration Parameters
!C4 (B1 Channel Mapping)

Enables data calls to be made and accepted on the B1-channel. If !C5 is set to 0 the outgoing call SETUP
message will contain a Channel Identification Information Element set to B1-channel only.

Value

Description
0 Incoming data calls on the B1-channel are rejected with ‘channel not

acceptable’ as the cause.
4 (default) Incoming data calls on the B1-channel are accepted provided no other
data call is present.

!C5 (B2 Channel Mapping)

Enables data calls to be made and accepted on the B2-channel. If !C4 is set to 0 the outgoing call SETUP
message will contain a Channel Identification Information Element set to B2-channel only.

Value

Description
0 Incoming data calls on the B2-channel are rejected with ‘channel not

acceptable’ as the cause.
4 (default) Incoming data calls on the B2-channel are accepted provided no other
data call is present.

If both !C4 and !C5 =0 no data calls will be made or received.

Note:
!C6 (MSN Directory Number)

Also refer to ISDN MSN (Section 4.3.5).
If there is a number saved in this register upon receipt of an incoming data call, the CMX228 will check for the

presence of a Called Party Number Information Element. If present it will compare the number with that
saved in the !C6 register. If they match, the call will be accepted, i.e. a ‘RING’ indication (RI pin is raised, then
lowered after 3s) is returned to the DTE. If the Called Party Number Information Element and saved MSN do
not match, the call is ignored. The command is entered as follows:

AT!C6=“nnnn”<CR> if no digits are present within the quotes, the MSN is cleared.
Up to 23 digits may be entered.

!C7 (TEI selection)

Selects the fixed or negotiated TEI used on the ISDN link. Note that the value of !C7 only takes effect when
the ISDN interface goes from de-activated to activated.

Value

Description
0-63 Fixed TEI, 0 to 63.
64 (default) Negotiated TEI.

!C8 (ISDN Line Failure Detection enable/disable)

Enables or disables Line Failure Detection. (Refer to Section 4.3.3).
Value

Description
0 Line Failure Detection disabled.
1 (default) Line Failure Detection enabled.

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4.7 Data Operation

4.7.1 Incoming B-Channel Data Calls

All incoming data calls which have valid channel use and MSN are directed to the data port and cause ‘RING’
followed by the digits of the calling party number and the calling party sub-address (if received in the SETUP
message) to be returned to the DTE. The Ring Indicator (RI) pin is also raised, and then lowered after 3s.
‘RING’ text and the raising of RI for 3s is repeated every 6s until the call is cleared or answered, provided
S0=0. If S0=1 then only one RING will appear at the DTE and the RI line will be raised only once, as a
CONNECT message will be sent to the network.

4.7.2 Outgoing B-Channel Data Calls

Outgoing calls are requested specifying either B-channel unless channel mapping is enabled via !C4 and !C5
registers. The SETUP message is sent without High Layer Compatibility or Low Layer Compatibility and with
the following Bearer Capability:

CCITT coding standard
Unrestricted digital
Circuit mode
64k information transfer rate

If there is a saved MSN in !C6 register all outgoing call SETUP messages will contain the saved number in a
Calling Party Number Information Element.

4.7.3 X.25 Data Calls on the D-Channel

When D-channel data is selected (via Hayes register %A2), B-channel data calls cannot be made. Any
incoming B-channel data calls will be rejected with ‘Busy’.

4.7.4 Connected Calls

Once a call is connected to the digital port, whether it was incoming or outgoing, the DCD pin is set high to
indicate that the call is connected (providing &C0 command is not given). If the DCD pin is set high, the LED3
pin will be set low.

4.7.5 Call Clearing

The call is cleared either by the ATH command or by the ISDN network. When the call has been cleared, the
DCD pin is set low and the LED3 pin is set high (providing the &C0 command is not given).

4.8 Application Programmer's Interface

Details of this will be supplied to customers under a Non-Disclosure Agreement.
The following Memory Map indicates the main code areas used on the CMX228:

Function Start Hex Address End Hex Address

Code Space 000 000 01F FFF
External RAM 020 000 03F FFF
API area 0C0 000 0EF FFF
AMD79C30 ISDN Interface Chip 0F0 000 0F0 0FF
PSB21525 HDLC Driver Chip 0F0 100 0F0 1FF
Reserved 0F0 200 0FF FFF

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4.9 Hardware Description

4.9.1 LED Status Indicators (LED1 to LED9, and ILFI)
LED1 (HK1)
LED2 (AA)

Auto Answer indication).

LED3 (DCD)

connected to this port.

LED4 (RTS)

To Send).

LED5 (RXD)
LED6 (TXD)
LED7 (DTR)
LED8 (AR)
LED9 (CN1)

is high when an ISDN Link Failure is Indicated, low when the link is operational.

ILFI

The functions of the LED and ILFI indicators are set out in the table below:

is low when the POTS port is off-hook, high when on-hook.

indicates that register S0 has been set to 1 or more when low and set to 0 when high (RS232

is low when a call is connected via the RS232 port (if &C0 is set to '1'), high when a call is not

is low if RTS on the RS232 port is active and vice versa, indicating flow control (RS232 Ready

is low if data is being sent to the DTE (RS232).
is low if data is being received from the DTE (RS232).
is low if the de-bounced DTR line on the RS232 port is active and vice versa.

is pulsed high and low until the ISDN line is activated, when it remains low constantly.

is high when the POTS port is connected to the ISDN network, low when not connected.

Pin No. Designation POTS port RS232 port

12 LED1 Off-Hook ~
13 LED2 ~ Auto-Answer
14 LED3 ~ Carrier Detect
15 LED4 ~ Ready to Send
16 LED5 ~ Receive Data
17 LED6 ~ Transmit Data
18 LED7 ~ Data Terminal Ready
19 LED8 ISDN Line Activated ISDN Line Activated
21 LED9 Call Connected ~
54 ILFI ISDN Line Failure Indicator ISDN Line Failure Indicator

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5. Application Notes

5.1 General

The CMX228 is intended for use as part of an ISDN chipset. The MX-COM recommended hardware
implementation contains the following elements (refer to Figure 3):

‘S’ bus interface via RJ45 socket.
RJ11 analog telephone socket and analog circuitry.
ISDN line transformer.
AMD79C30 S-interface controller.
Single asynchronous RS232 interface via 9-way or 25-way D-type connector.
64K bytes external RAM.
16K Non-volatile memory.
Ten processor controlled LED indicator signals.
HDLC drivers for the 2 ISDN B-channels, both channels can be used for data transfer.

50V

5V

SIEMENS

PSB 21525

2X(HDLC & FIFO)

IOM2
BUS

AMD AM79C30

S/T CONTROLLER & PCM CODEC

FIFO & DLC Tx DTMF,RING,TONES

DISCRETE

POTS SLIC

POTS

port

HY 6281009

128K RAM

5 x Interface ICs

PARALLEL BUS

CMX605

RxDTMF

TxCLID,SPM

RING & TONES

BUS

C-BUS

16K EEPROM

2

IC

24C16

WATCHDOG

CMX228
4K RAM 128K ROM
PROTOCOL ENGINE

MAX 238
RS232 V24/1

RS232

port

TC 1232CO

10 x LEDS

S/T

12V

MOTOROLA

MC34063A

MC7805CT

PSU

31909x029

TRANSFORMER

Figure 3: Application Block Diagram

5.2 Approvals

The firmware and finite state machine embedded in the CMX228 have been used in products that have
gained ETSI CTR3 approval.

API
port

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6. Performance Specification

6.1 Electrical Performance

6.1.1 Absolute Maximum Ratings

Exceeding these maximum ratings can result in damage to the device.

Min. Max. Units

Supply (AVDD - AVSS), (DV
Voltage on any pin to AVSS, DV
Current into or out of any VDD or V
Current into or out of any other pin -20 10 mA

S1 Package (QFP)

Total Allowable Power Dissipation at T

Derating above 25°C 17 mW/°C above 25°C
Storage Temperature -55 125 °C
Operating Temperature -40 85 °C

6.1.2 Operating Limits

Correct operation of the device outside these limits is not implied.

Supply:

- AVSS)

(AV

DD

(DV
(DV

DD0
DD1

- DV

- DV

SS0
SS1

)
)

Operating Temperature -40 +85 °C
32MHz Xtal Frequency Tolerance -100 +100 ppm

DD0

- DV

SS0

SS0

or DV

pin

SS

), (DV

SS1

AMB

- DV

DD1

= 25°C

)

SS1

-0.3 7.0 V
V

-0.3

DD

+ 0.3

V

-30 100 mA

1300 mW

Notes Min. Max. Units

2.7 5.5 V

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6.1.3 Operating Characteristics

Details in this section represent design target values and are not currently guaranteed.

For the following conditions unless otherwise specified:
Xtal Frequency = 32MHz ± 100ppm, AV

DD

= DV

DD0

= DV

= 3.0V to 5.0V, T

DD1

= - 40°C to +85°C.

AMB

Notes Min. Typ. Max. Units
DC Parameters

IDD (total, operational)
IDD (total in HALT mode)
IDD (total in IDLE mode)

Digital Interface

Input logic "1" level 70%
Input logic "0" level 30%
Input leakage current (VIN = 0 to DVDD)
Output logic "1" level (lOH = 120µA)
Output logic "0" level (l
Input or Output leakage current (V

= 360µA)

OL

OUT

= VDD)

Xtal/Clock Input

'High' pulse width (t
'Low' pulse width (t

WXH

WXL

)

)
Risetime (tXR)
Falltime (tXF)
Period (t

CYK

)

1 25.0 45.0 mA
1 13.0 26.0 mA
1 12.0 mA

V

DD

V

DD

-10.0 +10.0 µA
V

DD

-1.0

V
400 mV
10 µA

2 10 125 ns
2 10 125 ns
2 10 ns
2 10 ns

2, 3 31.2468 31.2531 ns

Notes:

1. Not including any current drawn by external circuitry.

2. Timing for an external in put to the XTAL pin.

3. A fundamental cut crystal is recommended.

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6.1.3.1 Timing Diagrams

(1) Read Operation

t

WSTH

ASTB

A8-A19

t

SAST

t

HSTLA

t

DSTID

t

DRST

A/D0-A/D7

RD

(2) Write Operation

ASTB

A8-A19

A/D0-A/D7

t

WSTH

t

DWST

t

t

HWA

HRA

t

DRA

t

t

HRID

HWOD

t

DAID

t

DSTR

t

DAR

t

SAST

t

HSTLA

t

DSTW

t

DAW

t

DSTOD

t

FRA

t

DRID

t

WRL

t

DWOD

t

SODW

WR

t

Figure 4: External Memory Access Timing

WWL

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CLOCK OUTPUTTIMING

ASTB

INTERRUPT INPUTTIMING

NMI

RESET INPUTTIMING

RST

EXTERNAL CLOCKTIMING

t

CLH

t

CLR

t

CYCL

t

WNIH

t

WRSH

t

CLL

t

CLF

t

WNIL

t

WRSL

t

WXH

XTAL

t

XR

t

Figure 5: Miscellaneous Timing

CYK

t

WXL

t

XF

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6.1.3.2 AC Timing Parameters

For the following conditions unless otherwise specified:
Xtal Frequency = 32MHz, AV

DD

= DV

DD0

= DV

= 3.0V to 5.0V, T

DD1

= - 40°C to +85°C.

AMB

6.1.3.2.1 Read/Write operation (1/2)

Where: T = t

(system clock cycle time)

CYK

a = 1 (during address wait), otherwise, 0
n = Number of wait states (n = 2)

Parameter Symbol Conditions Min. Max. Units

t

Address setup time

ASTB high-level width

Address hold time to (ASTB↓)

Address hold time (to
Delay from address to

Address float time (to

RD

RD

RD

↑

)

↓

↓

)

Delay from address to data input

Delay from ASTB↓ to data input

Delay from

Delay from ASTB↓ to
Data hold time (to
Delay from

↓

to data input

RD

RD

↑

to address active

RD

RD

↑

↓

)

VDD = +5.0V ± 10%

SAST

t

VDD = +5.0 V ± 10%

WSTH

t

VDD = +5.0 V ± 10%

HSTLA

t

HRA

V

t

DAR

t

FRA

t

VDD = +5.0V ±10%

DAID

t

DSTID

V

t

DRID

t

DSTR

t

HRID

V

t

DRA

0.5T - 14 ns
= +5.0V ±10%

DD

0 ns

VDD = +5.0V ±10%

= +5.0 V ±10%

DD

0.5T - 9 ns

0 ns

= +5.0 V ±10%

DD

After program is read
After program is read

V

= +5.0 V ±10%

DD

After data is read
After data is read

Delay from

RD

↑

to ASTB↑

RDlow-level width

Address hold time (to
Delay from address to

WR

WR

↑

)

↓

Delay from ASTB↓ to data output

Delay from
Delay from ASTB↓ to

WR

↓

to data output

↓

WR

t

DRST

t

V

WRL

t

HWA

VDD = +5.0V ±10%

t

DAW

t

DSTOD

t

DWOD

t

DSTW

0.5T - 17 ns
= 5.0 V ±10%

DD

0.5T - 14 ns

VDD = +5.0V ±10%

0.5T - 11 ns

0.5T - 9 ns

(0.5 + a) T - 15
(0.5 + a) T - 31

(0.5 + a) T - 17
(0.5 + a) T - 40

0.5T - 24

0.5T - 34

(1 + a) T - 9
(1 + a) T - 15

(2.5 + a + n) T - 37

(2 + n) T - 40

(1.5 + n) T - 50

0.5T - 8

0.5T - 12

0.5T - 8

1.5T - 12

(1.5 + n) T - 30
(1.5 + n) T - 40

(1 + a) T - 5
(1 + a) T - 15

0.5T + 19

ns

ns

ns

ns

ns

ns

ns

ns

ns

(2.5 + a + n) T - 52

ns
ns

(2 + n) T - 60

ns
ns

(1.5 + n) T - 70

ns

ns
ns

ns
ns

ns

ns

ns

ns
ns

0.5T + 35

ns

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6.1.3.2.2 Read/Write operation (2/2)

Parameter Symbol Conditions Min. Max. Units

Data setup time (to

Data hold time (to

Delay from

WR low-level width

WR

WR

WR

↑

to ASTB↑

VDD = +5.0 V ± 10%

↑

)

Note 1

↑

)

SODW

t

VDD = +5.0V ± 10%

HWOD

t

DWST

t

VDD = +5.0V ± 10%

WWL

0.5T - 12 ns

(1.5 + n) T - 30
(1.5 + n) T - 40

0.5T - 5

0.5T - 25

(1.5 + n) T - 30
(1.5 + n) T - 40

ns

ns

ns

ns

ns

ns

t

Note:

1. Hold time includes the time during which V

OH1

and V

are held under the load conditions of CL = 50pF

OL1

and RL = 4.7kΩ.

6.1.3.2.3 Miscellaneous timing

Where: T = t

(system clock cycle time)

CYK

a = 1 (during address wait), otherwise, 0.
n = Number of wait states (n = 2).

Parameter Symbol Conditions Min. Max. Units

t

ASTB cycle time
ASTB low-level width

ASTB high-level width

ASTB rise time

ASTB fall time

NMI low-level width
NMI high-level width

low-level width

RST

high-level width

RST

CYCL

t

V

CLL

t

V

CLH

t

V

CLR

t

V

CLF

t

WNIL

t

WNIH

t

WRSL

t

WRSH

nT ns

DD

DD

DD

DD

10 µs
10 µs
10 µs

10 µs

= +5.0 V ± 10% 0.5 t

0.5 t

= +5.0 V ± 10% 0.5 t

0.5 t

= +5.0 V ± 10%

= +5.0 V ± 10%

10

10

CYCL
CYCL

CYCL
CYCL

- 10

- 20

- 10

- 20

ns

ns

ns

ns
ns

20

ns
ns

20

ns

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6.2 Packaging

Figure 6: 80-pin QFP Mechanical Outline:

Order as part no. CMX228S1

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