V22 and Bell 212A Modem
CMX644A
1.3
Signal List
CMX644A
D2/D5/P4
Pin No.
1
2
Signal
Name
XTALN
XTAL/CLOCK
Type
O/P
I/P
The inverted output of the on-chip oscillator.
The input to the on-chip oscillator, for external
Xtal circuit or clock.
The ‘C-BUS’ serial clock input. This clock,
produced by the
µController,
is used for the
transfer timing of commands to and from the
device.
The ‘C-BUS’ serial data input from the
µController.
Data is loaded into this device in 8-
bit bytes, MSB (B7) first, and LSB (B0) last,
synchronised to the SERIAL CLOCK.
The ‘C-BUS’ serial data output to the
µController.
The transmission of REPLY DATA
bytes is synchronised to the SERIAL CLOCK
under control of the CSN input. This 3-state
output is held at high impedance when not
sending data to the
µController.
The ‘C-BUS’ data loading control function: this
input is provided by the
µController.
Data
transfer sequences are initiated, completed or
aborted by the CSN signal.
This output indicates an interrupt condition to the
µController
by going to a logic ‘0’. This is a
‘wire-ORable’ output, enabling the connection of
up to 8 peripherals to 1 interrupt port on the
µController.
This pin has a low impedance
pulldown to logic ‘0’ when active and a high
impedance when inactive. An external pull-up
resistor is required.
The output of the transmit gain control.
The output of the line driver amplifier.
The inverting input to the line driver amplifier.
The inverted output of the line driving amplifier.
Pins TXO and TXON provide symmetrical
outputs for use with a balanced load to give
sufficient Tx line signal levels even at low VDD.
Description
3
SERIAL CLOCK
I/P
4
COMMAND DATA
I/P
5
REPLY DATA
T/S
6
CSN
I/P
7
IRQN
O/P
8
9
10
11
TOP
TXO
TXN
TXON
O/P
O/P
I/P
O/P
©
2000
Consumer Microcircuits Limited
4
D/644A/6
CMLMICRO [ CML MICROCIRCUITS ]
