The signal lines of an input port are identified by the prefix IB.
The next character is a numerical designation for the port. The last
numeric character defines bits O, 1, 2, or 3. Bit O is the least
significant bit, and bit 3 is the most significant bit. For example,
signal line IB23 represents the most significant bit, 3, of input port
2. Similarly, OB23 represents the most significant bit, 3, of output
Table 5-1 lists the input ports and the I/O bus selections that
result from the output control (OCO thru OC3) commands. These control
lines select a port or I/C bus either by controlling internal micro-
processor multiplexer or by externally driving a decoder residing on
control CCA A7. Table 5-2 lists the output ports. Both tables pro-
vide a brief description of port functions.
The microprocessor OCO thru OC3 lines perform the additional func-
tions of selecting a page of program read only memory (ROM) (program-
mer memory CCA A4), and generating miscellaneous control strobes in
conjunction with the I/O bus and the IN or OUT strobes. The miscel-
laneous control strobes are listed and described in table 5-3.
Timing for the various receiver control operations is provided by
circuits on control CCA A7.
CCA A7 provides the following receiver
The 1.67-MHz microprocessor clock (CCA A1).
The 26-kHz and 3.25-kHz front panel control conversion clocks.
The 6.5-kHz and 13.0-kHz external interface clocks.
Receiver control adc and audio CCA A3 accepts intercept receiver
and df receiver audio, and responds to receiver control front panel
volume adjustments by providing the desired level of output audio.
This audio is applied to CCA A7 for distribution to the platform
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