CMX625
ISDN TA POTS Interface
D/625/2 July 2001
Advance Information
Features
•
SPM and Ringing Voltage Generators
•
Integrated DTMF Decoder/Encoder
•
V.23/Bell 202 FSK/Tone Generator
•
Selectable A-Law/µ-Law PCM Codec
•
IOM-2 Interface Terminal Mode and
Non-Terminal Mode (Line Card Mode)
Applications
•
ISDN NTUs with Analogue Ports
•
ISDN Line Cards
•
Wireless Local Loop Termination Cards
•
ISDN Terminals with Additional POTS Ports
•
PC based ISDN Cards with Telephone Ports
•
Billing/SPM Systems
IOM is a trademark of Siemens AG
1.1
Brief Description
The CMX625 is an integrated telecom tone generator, DTMF encoder/decoder and PCM Codec-Filter
designed for ISDN interfaces, Wireless Local Loop and other digitised speech systems. The tone
generator covers a wide range of pre-programmed tones used in analogue phone systems. Three outputs
are provided: Ringing signals, In-band tones or FSK data, and 12kHz/16kHz Subscriber Metering pulses.
The PCM Codec-Filter performs voice digitisation and reconstruction and incorporates band limiting and
smoothing with selectable A-law or µ-law companding following ITU-T recommendation G.711. The
DTMF decoder presents the serial bus interface with the DTMF dialling information received from the
telephone user and the tone generator sends the appropriate DTMF tones to this POTS interface. Other
tone standards supported are: Fax and Modem ‘answer’ and ‘originate’, ITU-T ‘R1’ and ‘R2’ signals, dual
tones for CIDCW and 'On-Hook' signalling systems and sufficient tones for simple melody generation.
The IOM -2 (ISDN Oriented Modular revision 2) industry standard serial bus provides the digital interface
to other telecommunications ICs and supports both Terminal and non-Terminal (or Line Card) modes.
The CMX625 is compatible with the CMX635 ISDN Subscriber Processor and can be used to provide the
additional POTS port. It is available in both DIP and SSOP packages.
®
2001 Consumer Microcircuits Limited
ISDN TA POTS Interface
CMX625
CONTENTS
Section
1.1
1.2
1.3
1.4
1.5
Page
Brief Description ..................................................................................... 1
Block Diagram ......................................................................................... 3
Signal List ................................................................................................ 4
External Components ............................................................................. 6
General Description ................................................................................ 7
1.5.1 IOM™-2 Serial Bus Interface ..................................................... 7
1.5.2 Terminal Mode (TE).................................................................... 8
1.5.3 Non-Terminal Mode (non-TE) ................................................. 10
1.5.4 Monitor Channel Handshake Protocol................................... 11
1.5.5 Monitor Channel Identification Command ............................ 13
1.5.6 PCM Codec-Filter ..................................................................... 13
1.5.7 Rx Input Amplifier .................................................................... 14
1.5.8 Tx Output Buffer ...................................................................... 14
1.5.9 Tone/FSK Encoder and Tone Encoder .................................. 14
1.5.10 SPM Generator ......................................................................... 17
1.5.11 Transmit Signal Control .......................................................... 17
1.5.12 Tx UART .................................................................................... 18
1.5.13 DTMF Tone Decoder ................................................................ 19
1.5.14 Register Set .............................................................................. 20
1.5.15 Programming the CMX625 ...................................................... 20
1.5.16 Glossary.................................................................................... 22
Application Notes.................................................................................. 23
1.6.1 Telecom Tones ......................................................................... 23
Performance Specification................................................................... 27
1.7.1 Electrical Performance ............................................................ 27
1.7.2 Packaging ................................................................................. 33
1.6
1.7
2001 Consumer Microcircuits Limited
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D/625/2
1.2
ISDN TA POTS Interface
RESET
FSC
TE/NTE
SA0
SA1
SA2
DS
DCL
DD
DU
IRQN
Block Diagram
IOM
®
-2 Serial Bus Interface
SETUP &
MODE Registers
STATUS
Register
PCM Codec
Registers
Interrupt
Generator
2001 Consumer Microcircuits Limited
FSK / TONES
Tx Registers
Rx Input
Amplifier
DTMF
Tone
Decoder
STATUS
& IRQ
BUS
SPM Generator
SPM
RXN
RXP
Enable
RXO
Tx Output
Buffer
ROM
STATUS
& IRQ
Tone Encoder
Tx UART
Tone / FSK
Encoder
Vbias
Enable
TXN
TXO
TXON
Figure 1 Block Diagram
3
V
DD
V
BIAS
Tx Signal
Control
RING
TONEFSK
V
SS
PCM ADC
A-law / -law
Analogue Loopback
PCM DAC
A-law / -law
DAC OUT
D/625/2
CMX625
ISDN TA POTS Interface
CMX625
1.3
Signal List
CMX625
D5/P4
Pin No.
1
Signal
Name
FSC
Type
I/P
The IOM-2 Frame Synchronisation Clock. This is an 8kHz
clock indicating the start of the frame. FSC is generated
by the upstream device. See section 1.5.1, 1.5.2 and
1.5.3.
The IOM-2 Data Clock. It is used to clock data on and off
the bus and operates at 1.536MHz for Terminal mode
(TE) or 4.096MHz for non-Terminal mode (non-TE or Line
Card mode). DCL is generated by the upstream device.
When the bus is deactivated, DCL is held in a low state.
See section 1.5.1, 1.5.2 and 1.5.3.
The IOM-2 Data Downstream, receives data from the
network. When the bus is deactivated or when data is not
being transmitted, DD is high impedance. The IC Channel
Bus Reversal (TE mode only) allows IC1 and IC2 data to
be transmitted on the DD pin. See section 1.5.1, 1.5.2,
1.5.3 and 1.5.6. An external pull-up resistor is required.
The IOM-2 Data Upstream, transmits data to the network.
When the bus is deactivated or when data is not being
transmitted, DU is high impedance. The IC Channel Bus
Reversal (TE mode only) allows IC1 and IC2 data to be
received on the DU pin. See section 1.5.1, 1.5.2, 1.5.3
and 1.5.6. An external pull-up resistor is required.
The IOM-2 two modes of operation: TE = 0 selects
Terminal mode. NTE = 1 selects Non-Terminal mode or
Line Card mode. See section 1.5.1, 1.5.2 and 1.5.3.
)
)
)
)
The IOM-2 Slot Address, provides one of 8 unique
addresses. It allows the device to be individually
addressed when more than one device is connected
to the IOM-2 bus. See section 1.5.2 and 1.5.3.
Description
2
DCL
I/P
3
DD
BI
4
DU
BI
5
TE/NTE
I/P
6
7
8
9
SA0
SA1
SA2
DS
I/P
I/P
I/P
I/P
The IOM-2 Device Select pin (NTE mode only). Allows two
CMX625 devices sharing a Slot Address to be individually
addressed. DS = 0 selects device one. DS = 1 selects
device two. See section 1.5.2 and 1.5.3.
The external reset pin clears all the registers. (RESET=1)
A ‘wire-Orable’ output Interrupt Request. This output is
pulled down to V
SS
when active and is high impedance
when inactive. An external pull-up resistor is required.
10
11
RESET
IRQN
I/P
O/P
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ISDN TA POTS Interface
CMX625
CMX625
D5/P4
Pin No.
12
13
14
15
16
Signal
Name
V
SS
RXP
RXN
RXO
V
BIAS
Type
Power
I/P
I/P
O/P
O/P
Description
The negative supply rail (ground).
The non-inverting input of the receive op-amp.
The inverting input of the receive op-amp.
The output of the receive op-amp.
An internally generated bias voltage of V
DD
/2, except
when the device has been reset, V
BIAS
will discharge to
V
SS.
It should be decoupled to V
SS
by a capacitor
mounted close to the device pins.
The sinewave output of the Tones and FSK signal
generators.
The output of the buffer amplifier.
The inverting input to the buffer amplifier.
The inverted output of the buffer amplifier.
The output from the digital-to-analogue converter.
The square, trapezoidal and sinusoidal wave output from
the Ringing Signal Generator.
The sinewave output of the SPM signal generator.
The positive supply rail. Levels and thresholds within the
device are proportional to this voltage. It should be
decoupled to V
SS
by a capacitor mounted close to the
device pins.
17
18
19
20
21
22
23
24
TONEFSK
TXO
TXN
TXON
DAC OUT
RING
SPM
V
DD
O/P
O/P
I/P
O/P
O/P
O/P
O/P
Power
Notes:
I/P
O/P
BI
N/C
=
=
=
=
Input
Output
Bi-directional
No (external) Connection
This device is capable of detecting and decoding small amplitude signals. To achieve this V
DD
and V
BIAS
decoupling and protecting the receive path from extraneous in-band signals are very
important. It is recommended that the printed circuit board is laid out with a ground plane in the
CMX625 area to provide a low impedance connection between the V
SS
pin and the V
DD
and V
BIAS
decoupling capacitors.
2001 Consumer Microcircuits Limited
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D/625/2
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