1200/2400/4800bps MSK Modem
4
MX469
2. Signal List
Signal
P
1
DW
1
D3
1
Xtal/Clock
input
The input to the on-chip inverter, for use with either a
1.008MHz or a 4.032MHz Xtal or external clock. Clock
frequency selection is by the “Clock Rate” input pin. The
selection of this frequency will affect the operational Data
Rate of this device. Refer to Table 3. Operation of any
MX•COM IC without a Xtal or clock input may cause
device damage. To minimize damage in the event of a
Xtal/drive failure, it is recommended that a current
limiting device (resistor or fast-reaction fuse) be installed
on the power supply (V
DD
).
Output of the on-chip inverter.
A squarewave, produced on-chip, to synchronize the
input of logic data and transmission of the MSK signal
(See Figure 3).
When the transmitter is enabled, this pin outputs the
(140-step pseudo sinewave) MSK signal (See Figure 3).
With the transmitter disabled, this output is set to a high-
impedance state.
Serial logic data to be transmitted is input to this pin.
A logic ‘0’ will enable the transmitter (See Figure 3). A
logic ‘1’ at this input will put the transmitter into
powersave while forcing “TX Sync Out” to a logic ‘1’ and
“TX Signal Out” to a high-impedance state. This pin is
internally pulled to V
DD
.
The output of the RX Bandpass Filter. This output
impedance is typically 10k and may require buffering
prior to use.
The control of the RX function. The control of other
outputs is provided in Table 2
The output of the on-chip analog bias circuitry. Held
internally at V
DD
/2, this pin should be decoupled to V
SS
by a capacitor (C2). See Figure 2 and RX Enable notes.
This bias voltage is maintained under all powersave
conditions.
Negative supply (GND).
The recovered asynchronous serial data output from the
receiver.
The recovered synchronous serial data output from the
receiver. Data is latched out by the recovered clock,
available at the “RX Sync O/P”. (See Figure 4 and
Figure 6).
For 1200 and 2400bps operation only. When an MSK
signal is being received this output is a logic ‘1’. The
Carrier Detect signal should be ignored during 4800bps
operation.
The MSK signal input for the receiver. This input should
be coupled via a capacitor, C3.
Type
Description
2
3
2
3
2
3
Xtal
TX Sync
output
output
MX469P package discontinued
5
5
4
TX Signal
output
6
7
7
8
5
6
TX Data
TX Enable
input
Input
8
9
7
Bandpass
output
9
10
10
11
8
9
RX Enable
V
BIAS
Input
power
11
12
13
12
13
14
10
11
12
V
SS
Unclocked Data
Clocked Data
power
output
output
14
15
13
Carrier Detect
output
15
16
14
RX Signal
input
1998
MX-COM, Inc.
www.mxcom.com Tel: 800 638 5577 336 744 5050 Fax: 336 744 5054
Doc. # 20480081.010
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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CMLMICRO [ CML MICROCIRCUITS ]
