Technical description
4-26 HF SSB Transceiver 9323/9360/9390/9780 Technical Service Manual
Microprocessor and peripherals—control panel
Microprocessor
The microprocessor IC2 contained on the Display Panel PCB [1 04-02974] is
identical to the microprocessor IC101 on the Microprocessor and Audio PCB. For
details of operation see page 4-21, Microprocessor. To facilitate access to the
external non-multiplexed devices, IC3 is used by latching the lower order address
bits.
The following devices are connected to the bus:
• IC5—an EPROM containing an LCD display and control information. The
microprocessor selects the EPROM via the Program Store Enable signal IC2
pin 47.
• IC6—a RAM device supplementing the microprocessor's internal RAM. It is
selected via the Read or Write signals IC2 pins 30 and 31.
A voltage detector and reset circuit (IC10/A and associated components) resets the
microprocessor if the supply voltage ("A" rail) falls below 9 V.
I
2
C buses
There are two I
2
C bus lines:
• EXT I
2
C bus—this bus is used to communicate between the Display Panel
PCB IC2 pins 22 and 23 and the transceiver's microprocessor IC101 [1
04-02976] (see page 4-22, I2C buses).
• Local I
2
C bus—allows the microprocessor IC2 pins 20 and 21 to communicate
to an 8–bit In/Out port IC1 and E
2
PROM IC4. The In/Out port IC1 allows
communications from the keypad. IC4 contains the contrast and back light
settings for the control panel.
Keypad
The keypad consists of switches on a panel overlay (substrate) forming a 3 × 4
matrix. The rows and columns are connected to the Display Panel PCB [1
04-02974] via P1.
The columns are held low. One line is driven direct from IC2 pin 11. The
remaining three lines are buffered by open collector transistors V1, V2 and V3,
which are driven from pins 14, 13 and 12 respectively.
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