Half Duplex GMSK Modem
FX579
1.3
Signal List
Package
D4
Pin No.
1
2
Name
XTALN
XTAL/CLK
Signal
Type
O/P
I/P
The output of the on-chip oscillator.
The input to the on-chip oscillator for an external
Xtal circuit or clock.
) 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.
The internal circuitry bias line, held at �½ V
DD
,
this pin must be decoupled to V
SS
by a capacitor
mounted close to the pin.
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
.
Negative supply rail. Signal ground.
The Tx signal output. This signal should be
applied to an external RC before being applied to
the radio modulator.
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.
Two pins used by the modem's Rx level
measurement circuitry. A capacitor should be
connected from each pin to V
SS.
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.
Description
3
4
5
CLKDIVA
CLKDIVB
ACQUIRE
I/P
I/P
I/P
6
V
BIAS
O/P
7
RXIN
I/P
8
9
V
SS
TXOP
Power
O/P
10
BT
I/P
11
12
DOC1
DOC2
O/P
O/P
13
TXRXN
I/P
©
1996 Consumer Microcircuits Limited
4
D/579/4
CMLMICRO [ CML MICROCIRCUITS ]
