Technical description
HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual 4-21
Microprocessor and peripherals—transceiver
Microprocessor
1 04-02976 Sheets 1 and 2
The microprocessor IC101 on the Microprocessor and Audio PCB is an 80C552, a
member of the Intel 80C51 8–bit microprocessor family. The microprocessor has:
• 256 bytes of RAM
• no internal program memory
• two counter/timers
• eight 8–bit ADC inputs
• a watchdog timer
• I
2
C Bus
• an internal clock oscillator
The microprocessor operates in a conventional 8–bit data, 16–bit address
configuration. To minimise the pin count, the low-order address bits are
multiplexed with the data on pins 50 to 57 to produce a common 8–bit bus. The
chip IC102 is used to latch the low order address bits to facilitate access to the
external non-multiplexed devices.
The Address Latch Enable (ALE) signal IC101 pin 48 indicates to the latch when
the address is present on the bus. The high order address bits are provided directly
from IC101 pins 39 to 46.
The external devices that are connected to the bus are:
• IC103—an EPROM containing control software and the 9390 Radphone
channels; selected via the Program Store Enable (
) signals from IC101 pins 30 and 31
• IC105—E
2
PROM containing the programmed channels
• IC106—a triple-tone generator used to generate control tones (see page 4-23,
Tone generation)
The microprocessor is reset if the supply voltage ("A" rail) falls below 9 V. The
reset circuit consists of a voltage detector and power up reset circuit IC107B and
associated components.
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