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During remote operation, the receiver is controlled by the microcomputer, but in place of
instructions from the front panel, the instructions to the microprocessor are obtained from the
remote controller:
.
1. During the front panel scan, the microprocessor monitors the position of the LOCAL-
REMOTE switch. When this switch
is
in REMOTE, the microprocessor will branch to the remote
mode portion of the program so that instead of responding to front panel switches, it will look for
command words from the remote interface card (A6AI) ..
2. Commands from the remote controller are received by the Serial Asynchronous Inter-·
face Assembly A6Al. As each.command is received, an interrupt is sent to the microcomputer whidi
directS the microcomputer to branch to specific portions of the program (or subroutine) to carry
out the command. After responding to the command instructions, the microcomputer returns to the
normal remote mode program until a new set of commands or requests are received from the remote
controller.
3. When the remote controller contains data for receiver control (such as frequency, AGC,
or mode selection) the microcomputer stores the data in memory.(RAM), and. on completion of
remote data interrogation transfers the information to the receiver circuits.
4. When the remote controller command contains a request for receiver status, the micro-
processor accesses the corresponding receiver status information stored in memory (RAM) and sends
it via the Serial Synchronous Interface, Assembly .(A6Al) to the Remote Controller.
5. In addition, the microcomputer under program control periodically (every 25 ms) reads
. the receiver parameters froin memory (RAM) and continually updates the front panel displays.
.
.
: , ' .
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/
When a request
is
receivedfromtheremotecontroller during LOCAl operation, the micro-
processor will respond and return the stattis'ofthereceiveras described in the 'above paragraphs.
.
Remote commands received during LOCAL operation will be stored in memory but they will not be
acted upon unless the receiver is placed in REMOTE operation.
The microcomputer directs all operations and communicates with other receiver control
circuits through its 8 bit bi-directional data bus and the write/read and clock (ROMC) lines. The
ROMC
lines
indicate the type of instructions to be performed with the write and clock lines pro-
viding the necessary infonnation. The 8-bit bus provides both bi-directional data and unidirectional
address capability (to the Receiver). The operating control program is contained in the program
memory EPROMS (Erasable Program Read Only Memory). Temporary storage for receiver. settings
and for data computations is provided by the Working Random Access Memory (RAMs), which can
be written into and read out of by the CPU. These memories are addressed by the CPU, through the
static memory interface (SMI). The CPU sends the ROMC, write and clock signals to the SMI. The
SMI recognizes the ROMe code calling for a Memory Address operation. The SMI, in ·sequence; ad-
dresses the ROM or RAM over the memory address bus. Then it sends a read signal t9 the EPROM (if
it
is
addressed) or sends a read or write signal to the RAM (if it is addressed). The CPU places the data
to be read by the RAM'on the data bus or reads the data placed on the data bus by the ROM or RAM,
as appropriate.
The microcomputer (A6A2) also contains the RESET and RAM data retention circuitry.
The RESET circuitry generates reset signals when power is applied and turned off. This reset signal
is applied to the CPU. When power comes on, the CPU initializes all circuitry to its starting condition
and causes the program to start at its initial program address. When power is removed, due to power
turn-off or power failure, the reset signal to the CPU goes low. The CPU now causes the system to
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