FX809 FFSK Modem
Recovered Clock
CHECKSUM GEN/CHECK
Rx IN
FFSK RECEIVER
XTAL/CLOCK XTAL
CLOCK GENERATOR
Recovered Clock
BYTE COUNTER
DATA REGISTER 1
DATA REGISTER 2
Rx SYNC Detect
SYNC/SYNC DETECT
Rx SYNC Detect
Rx FREE FORMAT CS
REPLY DATA
SERIAL CLOCK
COMMAND DATA
C-BUS INTERFACE
AND
CONTROL LOGIC
Interrupt Enable
RX DATA BUFFER
TX DATA BUFFER
Rx Data Ready
Tx Data Ready
SYNC PROGRAM LOW – HIGH
Tx Idle
8-Bit Parallel Bus
ADDRESS DECODER
Rx SYNC Detect
Rx SYNC Detect
CONTROL REGISTER
STATUS REGISTER
WAKE
ADDRESS SELECT
Fig 1. FX809 FFSK Modem
VDD
FFSK TRANSMITTER
TX OUT VBIAS
VBIAS
AMP IN
–
+ UNCOMMITTED
AMPLIFIER
AMP OUT
V SS
INTERRUPT GENERATOR
IRQ
Brief Description
An intelligent, half-duplex, FFSK/MSK modem which operates under “C-BUS” control. In addition this modem provides software selectable checksum generation and error checking, in accordance with MPT1327. The FX809, using Interrupt and Status Register procedures, performs the ...