1200/2400/4800 Baud FFSK/MSK Modem
CMX469A
CMX469A
D3
E2
P6
Signal
Description
Pin
No.
13
14
15
16
Pin
No.
15
16
18
19
Pin
No.
14
15
17
16
Name
CARRIER
DETECT O/P
Rx SIGNAL I/P
Rx SYNC O/P
1200/2400
BAUD
SELECT
Type
O/P
I/P
O/P
I/P
When an FFSK/MSK signal is being received
this output is a logic ‘1’.
The FFSK/MSK signal input for the receiver. This
input should be coupled via a capacitor, C3.
A flywheel squarewave output. This clock will
synchronize to incoming Rx FFSK/MSK data.
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.
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).
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.
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).
18
21
19
CLOCK RATE
I/P
19
22
20
CARRIER
DETECT TIME
CONSTANT
BI
20
24
22
V
DD
PWR
4, 6,
17, 23
Notes:
4, 21
No internal connection, do not use.
I/P = Input
O/P = Output
BI = Bidirectional
PWR = Power
©
2001 Consumer Microcircuits Limited
6
D/469A/2
CMLMICRO [ CML MICROCIRCUITS ]
