Theory Of Operation; Controller Circuits; Overview; General - Motorola 6864115B62-C Detailed Service Manual

1.0

Controller Circuits

1.1

Overview

This section provides a detailed theory of operation for the radio and its components. The main radio
is a single board design, consisting of the transmitter, receiver, and controller circuits. The main
board is designed to accept one additional option board. This may provide functions such as secure
voice/data, voice storage or signalling decoder.
A controlhead is either mounted directly or connected by an extension cable. The controlhead
contains, LED indicators, a microphone connector, buttons and dependant of the radio type, a
display and a speaker. These provide the user with interface control over the various features of the
radio.
If no controlhead is mounted directly on the front of the radio, an expansion board containing circuitry
for special applications can be mounted on the front of the radio. An additional controlhead can be
connected by an extension cable.
In addition to the power cable and antenna cable, an accessory cable can be attached to a
connector on the rear of the radio. The accessory cable provides the necessary connections for
items such as external speaker, emergency switch, foot operated PTT, and ignition sensing, etc
1.2

General

The radio controller consists of 3 main subsections:
■
Digital Control
■
Audio Processing
■
Voltage Regulation.
The digital control section of the radio is based upon an open architecture controller configuration.It
consists of a microprocessor, support memory, support logic, signal MUX ICs, the On/Off circuit, and
general purpose Input/Output circuitry.
The controller uses the Motorola 68HC11FL0 microprocessor (U0101). In addition to the
microprocessor, the controller has 3 external memory devices. The 3 memory devices consist of a
32Kbyte SRAM (U0122), a 512Kbyte FLASH EEPROM (U0121), and a 16Kbyte EEPROM (U0111).
Note: From this point on the 68HC11FL0 microprocessor will be referred to as µP. References to a
controlhead will be to the controlheads with display.

THEORY OF OPERATION

Chapter 1