Consumer Microcircuits Limited CMX469AP6, CMX469AE2, CMX469AD3 Datasheet

CMX469A

1200/2400/4800 Baud

FFSK/MSK Modem

 2001 Consumer Microcircuits Limited

D/469A/2 May 2001 Provisional Issue

Features Applications

•• Full-Duplex FFSK/MSK Modem with

Separate Rx and Tx Enable Functions

•• Data-Over Radio

•• Personal/Cordless Telephone

•• Pin Selectable Data Rates:

1200, 2400 or 4800 Baud

•• Radio and General Applications

•• Narrowband Coax Data Channels

•• Pin Selectable Xtal/Clock Inputs:

1.008MHz or 4.032MHz

•• Two Way Radio (MPT1327) Signalling

•• Portable Data Terminals

•• Clock Recovery Facility

•• Carrier Detect Facility

•• Low Power Operation (2.0mA typ. at 3.0V)

1.1 Brief Description

The CMX469A is a single-chip CMOS LSI circuit which operates as a full-duplex 1200, 2400 or
4800 baud FFSK/MSK modem. The mark and space frequencies are 1200/1800, 1200/2400 and
2400/4800 Hz respectively. Tone frequencies are phase continuous; transitions occur at the zero
crossing point. A common Xtal oscillator with a choice of two clock frequencies (1.008MHz or

4.032MHz) provides baud-rate, transmit frequencies, and Rx and Tx synchronization.
The transmitter and receiver operate entirely independently, including the individual section

powersave functions. The CMX469A includes on-chip circuitry for Carrier Detect and Rx Clock
recovery, both of which are made available as output pins. Rx, Tx and Carrier Detect paths
contain bandpass filters to optimise signal conditions in each section of the modem. The
CMX469A demonstrates good sensitivity and bit-error-rate under adverse signal conditions. The
Carrier Detect time constant is set by an external capacitor, so that the product's performance
can be optimised in high noise environments. This low-power device operates from a single
supply between 2.7V and 5.5V, requires few external components and is available in a wide

variety of plastic packages.

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

 2001 Consumer Microcircuits Limited 3 D/469A/2

CONTENTS

Section

Page

1.0 Features and Applications.......................................................................2

1.1 Brief Description .......................................................................................2

1.2 Block Diagram ...........................................................................................4

1.3 Signal List...................................................................................................5

1.4 External Components...............................................................................7

1.5 General Description..................................................................................8

1.6 Application Notes......................................................................................9

1.7 Performance Specification.....................................................................10

1.7.1 Electrical Performance..............................................................10

1.7.2 Packaging....................................................................................16

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

 2001 Consumer Microcircuits Limited 4 D/469A/2

1.2 Block Diagram

Figure 1 Block Diagram

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

 2001 Consumer Microcircuits Limited 5 D/469A/2

1.3 Signal List

CMX469A

D3 E2 P6 Signal Description

Pin
No.

Pin
No.

Pin
No.

Name Type

1 1 1 CLOCK/XTAL I/P The input to the on-chip inverter, for use with

either a 1.008MHz or a 4.032MHz Xtal or an
external clock. Clock frequency selection is by
means of the CLOCK RATE pin. This affects the
operational data rate of the device. Operation of
any CML microcircuit without a Xtal or clock

input may cause device damage.
2 2 2 XTALN O/P The output of the on-chip inverter.
3 3 3 Tx SYNC O/P O/P A squarewave, produced on-chip, to

synchronize the input of logic data and

transmission of the FFSK/MSK signal.
4 5 5 Tx SIGNAL

O/P

O/P When the transmitter is enabled, this pin outputs

the FFSK/MSK signal. With the transmitter

disabled, this pin is set to a high-impedance

state.
5 7 6 Tx DATA I/P I/P The serial logic data to be transmitted is input to

this pin.
6 8 7 Tx ENABLEN I/P A logic ‘0’ will enable the transmitter. A logic ‘1’ at

this input will put the transmitter into powersave

whilst forcing Tx SYNC OUTPUT to a logic ‘1’

and Tx SIGNAL OUTPUT to a high-impedance

state. This pin is internally pulled to V

DD

.

7 9 8 BANDPASS

O/P

O/P The output of the Rx Bandpass Filter. This output

impedance is typically 10k

Ω and may require

buffering prior to use.
8 10 9 Rx ENABLE I/P The control of the Rx function
9 11 10 V

BIAS

BI The output of the on-chip analogue bias circuitry.

Held internally at V

DD

/2, this pin should be

decoupled to V

SS

by a capacitor (C2). This bias
voltage is maintained under all powersave
conditions.

10 12 11 V

SS

PWR Negative supply rail (GND).

11 13 12 UNCLOCKED

DATA O/P

O/P The recovered asynchronous serial data output

from the receiver.

12 14 13 CLOCKED

DATA O/P

O/P The recovered synchronous serial data output

from the receiver. Data is latched out by the
recovered clock, available at the Rx SYNC O/P.

1200/2400/4800 Baud FFSK/MSK Modem CMX469A

 2001 Consumer Microcircuits Limited 6 D/469A/2

CMX469A

D3 E2 P6 Signal Description

Pin
No.

Pin
No.

Pin
No.

Name Type

13 15 14 CARRIER

DETECT O/P

O/P When an FFSK/MSK signal is being received

this output is a logic ‘1’.

14 16 15 Rx SIGNAL I/P I/P The FFSK/MSK signal input for the receiver. This

input should be coupled via a capacitor, C3.

15 18 17 Rx SYNC O/P O/P A flywheel squarewave output. This clock will

synchronize to incoming Rx FFSK/MSK data.

16 19 16 1200/2400

BAUD

SELECT

I/P A logic ‘1’ on this pin selects the 1200 baud

option. Tone frequencies are: one cycle of
1200Hz represents a logic ‘1,’ one-and-a-half
cycles of 1800Hz represents a logic ‘0.’

A logic ‘0’ on this pin selects the 2400 baud
option. Tone frequencies are: one-half cycle of
1200Hz represents a logic ‘1,’ one cycle of
2400Hz represents a logic ‘0.’ This function is
also used, in part, to select the 4800 baud
option. This pin has an internal 1M

Ω pullup

resistor.

17 20 18 4800 BAUD

SELECT

I/P A logic ‘1’ on this pin combined with a logic ‘0’ on

the 1200/2400 BAUD SELECT pin will select the
4800 baud option (1M

Ω pulldown resistor).

Tone frequencies are: one-half cycle of 2400Hz
represents a logic ‘1,’ one cycle of 4800Hz
represents a logic ‘0.’ Operation at 4800 baud is
only achieved by using a 4.032MHz Xtal or
clock.

18 21 19 CLOCK RATE I/P A logic input to select and allow the use of either

a 1.008MHz or 4.032MHz Xtal/clock. Logic ‘1’ =

4.032MHz, logic ‘0’ = 1.008MHz. This input has
an internal pulldown resistor (1.008MHz).

19 22 20 CARRIER

DETECT TIME

CONSTANT

BI Part of the carrier detect integration function. The

value of C4 connected to this pin will affect the
carrier detect response time and hence noise
performance.

20 24 22

V

DD

PWR Positive supply rail. A single 2.7 to 5.0 volt

supply is required. This pin should be decoupled
to V

SS

by a capacitor (C5).

4, 6,

17, 23

4, 21

No internal connection, do not use.

Notes: I/P = Input O/P = Output BI = Bidirectional PWR = Power