X-2 Technical Service Manual Technical Description 4-13
Publication No: 15-02047
4.5 Micro and Peripherals
4.5.1 Microcontroller
The microcontroller monitors all input lines and outputs commands to
various parts of the transceiver according to the information received and the
program stored in the ROM.
The microcontroller IC403 is a member of Motorola's MC68HC05 family.
The 8-bit microcontroller contains CPU, RAM, ROM, A/D, Pulse Length
Modulated Outputs, I/O, serial Communications interface, Timer system and
Watchdog.
4.5.2 I
2
C Bus
The serial data ports of the microcontroller IC403 pins 42 (data) and 44
(clock) provide the I
2
C bus to communicate to the following peripherals:
IC405 - I
2
C Bus/16 bit output driver
Commands from the microcontroller via the I
2
C bus, select the outputs of
IC405 to control PTT, USB/LSB, TUNE, MUTE, AGC CLAMP, BCD lines
for antenna control, UNLOCK 1 and 2 Leds, MIC enable and TX tones
enable.
IC404 - EEprom
A non-volatile memory device that provides the microcontroller with the
programmed channel information.
IC1-I
2
C bus/8 bit input
Provides the microcontroller with the front panel channel and clarifier control
functions.
IC5 and IC11
The PLL integrated circuits which control VCO1 and VCO2.
4.5.3 PA Control Bus
A separate serial data bus is provided from the microcontroller (pins 37 and
38) to control an 8 bit driver IC1 on the PA PCB. This enables the
microcontroller to select:
• the PA filters
• Antenna 1 or 2
• and the Tx/Rx changeover relay.
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