CMX615
Digital Line to
POTS Interface
D/615/4 December 1999
Provisional Issue
Features
•
Pre-Programmed Tone Generators
•
Fully Integrated DTMF Encoder
•
SPM Generator
•
Simple Serial Control Interface
•
‘Zero-Power’ (1µA) Standby Mode
•
3.58MHz Xtal/Clock
•
V23/Bell 202 FSK Generator
•
Digital Ringing Voltage Generator
Applications
•
Digital Line to POTS Interface
•
Subscriber Terminal Adapters
•
Wireless Local Loop
•
Computer Telephony Integration
•
Telephone/Radio Patch Systems
•
Pair Gain Systems
•
Billing/SPM Systems
1.1
Brief Description
The CMX615 is an integrated telecom tone generator and DTMF encoder designed for ISDN interfaces,
Wireless Local Loop and Analogue to Digital Phone Conversion systems. The tone generator covers an
extensive range of pre-programmed tones used in analogue phone systems (POTS). Three outputs are
provided: ‘Ringing signals’, ‘In-band tones or FSK data’, and ‘12kHz/16kHz Metering pulses’. Simple software
control facilitates the interface to a wide range of commonly used µCs and SLICs, enabling a comprehensive
analogue telephone line presentation.
The DTMF encoder generates the appropriate DTMF tones for the POTS interface. DTMF tone pairs can be
encoded along with each tone singly or with other dual tone signals, such as those used in CIDCW systems
and ‘On Hook’ signalling systems.
Other tone standards supported are: Fax and Modem ‘answer’ and ‘originate’, ITU (CCITT) ‘R1’ and ‘R2’
signals, and sufficient tones for simple melody generation. Communication to and from the host µController is
performed by a ‘C-BUS’ serial interface, which is compatible with the ‘SPI’ interface.
©
1999
Consumer Microcircuits Limited
Digital Line to POTS Interface
CMX615
CONTENTS
Section
Page
1.1 Brief Description.........................................................................................1
1.2 Block Diagram ............................................................................................3
1.3 Signal List ...................................................................................................4
1.4 External Components.................................................................................6
1.5 General Description....................................................................................7
1.5.1 Xtal Osc and Clock Dividers.......................................................7
1.5.2 Uncommitted Amplifier...............................................................7
1.5.3 Tone/FSK Encoder and Tone Encoder
......................................7
1.5.4 SPM Generator
..........................................................................10
1.5.5 Transmit Operator.....................................................................10
1.5.6 Tx UART.....................................................................................10
1.5.7 ‘C-BUS’ Interface.......................................................................11
1.5.8 ‘C-BUS’ Registers......................................................................13
1.6 Application Notes .....................................................................................14
1.6.1 ‘Telecom Tones.........................................................................14
1.6.2 ‘C-BUS Timing...........................................................................17
1.7 Performance Specification.......................................................................21
1.7.1 Electrical Performance..............................................................21
1.7.2 Packaging..................................................................................25
©
1999
Consumer Microcircuits Limited
2
D/615/4
Digital Line to POTS Interface
CMX615
1.2
Block Diagram
Figure 1 Block Diagram
©
1999
Consumer Microcircuits Limited
3
D/615/4
Digital Line to POTS Interface
CMX615
1.3
Signal List
CMX615
D4/P3
Pin No.
1
Signal
Name
XTALN
Type
O/P
The output of the on-chip Xtal oscillator
inverter.
The input to the oscillator inverter from the
Xtal circuit or external clock source.
The ‘C-BUS’ serial clock input from the host
µ
C. See section 1.5.8
The ‘C-BUS’ serial data input from the host
µ
C.
A 3-state ‘C-BUS’ serial data output to the
host
µ
C. This output is high impedance when
not sending data to the host
µ
C.
The ‘C-BUS’ transfer control input provided by
the host
µ
C.
A ‘wire-ORable’ output for connection to a host
µ
C Interrupt Request input. This output is
pulled down to VSS when active and is high
impedance when inactive. An external pullup
resistor is required.
The negative supply rail (ground).
The sinewave output of the Tones and FSK
signal generators.
The sinewave output of the SPM signal
generator.
Description
2
XTAL/CLOCK
I/P
3
SERCK
I/P
4
COMDATA
I/P
5
REPDATA
T/S
6
CSN
I/P
7
IRQN
O/P
8
9
V
SS
TONEFSK
Power
O/P
10
SPM
O/P
©
1999
Consumer Microcircuits Limited
4
D/615/4
Digital Line to POTS Interface
CMX615
CMX615
D4/P3
Pin No.
11
Signal
Description
Name
V
BIAS
Type
O/P
An internally generated bias voltage of V
DD
/2,
except when the device is in ‘Zero Power’ mode
when V
BIAS
will discharge to V
SS
. It should be
decoupled to V
SS
by a capacitor mounted close
to the device pins.
The non-inverting input to the uncommitted
amplifier.
The inverting input to the uncommitted amplifier.
The output of the uncommitted amplifier.
The squarewave output of the Ringing Signal
generator.
The positive supply rail. Levels within the device
are proportional to this voltage. It should be
decoupled to V
SS
by a capacitor mounted close
to the device pins.
12
OPPIN
I/P
13
14
15
OPNIN
OPOUT
RING
I/P
O/P
O/P
16
V
DD
Power
Notes:
I/P
O/P
T/S
=
=
=
Input
Output
3-state Output
It is recommended that the printed circuit board is laid out with a ground plane in the CMX615 area
to provide a low impedance connection between the V
SS
pin and the V
DD
and V
BIAS
decoupling
capacitors.
©
1999
Consumer Microcircuits Limited
5
D/615/4
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