Half Duplex GMSK Modem
FX579
1.3
Signal List
Package
D4
Signal
Description
Pin No.
Name
XTALN
Type
O/P
1
2
The output of the on-chip oscillator.
XTAL/CLK
I/P
The input to the on-chip oscillator for an external
Xtal circuit or clock.
3
4
5
CLKDIVA
CLKDIVB
ACQUIRE
I/P
I/P
I/P
) Two logic level inputs that control the internal
) clock divider and hence the transmit and
) receive data rate (See Table 1).
A logic "1" applied to this input will set the Rx
level measurement and Rx clock extraction
circuitry to 'acquire' mode.
6
7
V
O/P
I/P
The internal circuitry bias line, held at ½ V
,
DD
BIAS
this pin must be decoupled to V by a capacitor
SS
mounted close to the pin.
RXIN
The Rx signal input from the radio's discriminator
via suitable signal and dc level adjustment. In
Rx this pin is internally held at
½ V
.
DD
8
9
V
Power
O/P
Negative supply rail. Signal ground.
SS
TXOP
The Tx signal output. This signal should be
applied to an external RC before being applied to
the radio modulator.
10
BT
I/P
A logic level input to select the modem 'BT' (the
ratio of the Tx filter -3dB frequency to the bit
rate). A logic "1" sets the modem to a BT of 0.5,
a logic "0" to a BT of 0.3.
11
12
DOC1
DOC2
O/P
O/P
Two pins used by the modem's Rx level
measurement circuitry. A capacitor should be
connected from each pin to V
.
SS
13
TXRXN
I/P
A logic level applied to this pin determines
whether the modem operates in Tx or Rx mode.
A logic "1" sets Tx mode. A logic "0" sets Rx
mode.
ã 1996 Consumer Microcircuits Limited
4
D/579/4
CMLMICRO [ CML MICROCIRCUITS ]
