TECHNICAL MANUAL FOR COMPACT VHF DSC RM2042

1 INTRODUCTION RM2042MICROPROCESSORThe microprocessor module contains as the central unit, the microprocessor IC, a fast 16 bit type, withits external program memory and RAM circuits.The microprocessor clock-signal is derived from an 8 MHz XTAL-oscillator.The non-volatile memory consist of a single 8kByte EEPROM, where the received messages and internalprogramable settings are stored.As the microcomputer operates with an asyncroneous bus-configuration, some external control logicis needed to generate the appropriate interrupt signals etc. This block includes the reset circuitry as well.Address selection of the individual peripheral devices is done by means of a 4 to 16 line address decoder.The answer back from these circuits to the microprocessor, is done via the uP control logic.The time division on the microprocessor is partially determined by the outputs from the programabletimers, and partially by the real time clock circuit.The real time clock circuit is operating with an external XTAL at 32.768kHz, and has a separate primarybattery back-up, to preserve the time settings of the equipment.The reference clock for the FSK decoder and encoder, is derived from a 4.9152MHz XTAL oscillator,which among others are devided down to a 1200Hz signal.Communication with the FSK-modem is done via an USART.The printer interface is made by means of a standard i/o port circuit, placed on the interface module, whilethe strobe pulse needed for the printer is generated by a few gates on this module.The serial communication with external equipment, is executed via three USART’s placed on the interfacemodule.An i/o port circuit, is used for the interface between the microprocessor and the different single bit controlsignals. The same circuit is used when the keyboard matrix are scanned.This module includes, as well, the +5V to -5V voltage converter, the output of which is used on the displaymodule for the LCD-display.The voltage for the keyboard light, for night illumination, are also turned on and off on this module.The switch S1 is used in service.DISPLAY UNITThe display unit consist of two circuit boards.One board connected directly to the microprocessor module. Which includes a D/A converter to controlthe DC-amplifiers for viewing angel control and display backlight control, and a socket for connectionto the display module.The display is a standard dot-matrix LCD-display module, which includes the necessary drivers andparallel communication circuits.Power on/off switch and AF-volume potentiometer is mounted on this unit as well.This unit has been developed to be used in RM2150/51 as well, the identity programming needed is madeby means of a jumper on P5.KEYBOARDThe keyboard module is a standard module for the 2100-series of products. It consist of a 4x7 keybordmatrix, and light emitting diodes used for night illumination of the keyboard.PAGE 1-7