Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 102

WJ-8718-19/FE HF RECEIVER CIRCUIT DESCRIPTION
3.3.6 DIGITAL CONTROL SECTION
Figure 3-7 is a block diagram of the Digital Control Section. The Digital
Control Section is mounted on the I/O Motherboard P.W. Assembly A6. As shown in
Figure 3-7, the Digital Control Section consists of six major modules: Synthesizer
Interface/Memory, A6A1; IF Interface, A6A2; Asynchronous I/O, A6A3; Serial I/O
Buffer, A6A4; Sync Serial Input/Output, A6A5; Front Panel Switch/Encoder, MFP-A1.
3.3.6.1 Synthesizer Interface/Memory (A6A1) (794275)
The Synthesizer Interface contains a microprocessor and memory which
serves as the control element for the Digital Control Section. The microprocessor is
interfaced to A6A2 and A6A3 via an address/data bus. Front panel commands are
processed by the microprocessor via the address/data bus and receiver control
commands are sent back out over the bus. Tuned frequency and BFO frequency latches
transfer tuning data from the microprocessor to the Synthesizer Section.
3.3.6.2 IF Interface (A6A2) (796032)
The IF Interface connects to the Digital Control Section microprocessor on
A6A1 via the address/data bus. The IF Interface receives control commands from the
Front Panel components and sends them to the microprocessor on A6A1 Receiver
control commands to select gain mode, bandwidth, detection mode and RF gain control
are passed from the microprocessor to the IF/Demodulator Section via latches on the
IF Interface.
3.3.6.3 Asynchronous I/O (A6A3) (796037)
The Asynchronous I/O interfaces the microprocessor on A6A1 with remote
control equipment. The I/O connects to the Digital Control address/data bus and
communicates with remote equipment via RS422 serial format. The Asynchronous I/O
will accept commands from the remote equipment and will transfer receiver parameters
to the remote equipment. Two external ports are provided. One connects to the
external controller. The other connects to a second receiver. A maximum of 15
receivers can be connected in this "serial" fashion to be controlled by the remote
equipment. J uie
3-3.6.4 Serial I/O Buffer, (A6A4) (794300)
The Serial I/O Buffer performs two functions. First it interfaces the
microprocessor on A6A1 with the Frequency Extender. Data lines from the
address/data bus pass directly to the Frequency Extender to transfer frequency tuning
data words. An analog digital converter develops the analog tuning voltage to tune
the Preselector in the Frequency Extender. Second, the Serial I/O buffer functions as
a buffer/interface between the Sync Serial I/O and external remote control equipment
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