Microcontroller - Tait T880 II Series Adjustment Manual

C2.4 T881 Circuit Operation
2.2

Microcontroller

(Refer to the microcontroller circuit diagram (sheet 8) in Section 6.2.)
12.8MHz
Clock
External
Converter
Serial
Port
CTCSS Tone
Overall system control of the T881 is accomplished by the use of a member of the 80C51
family of microcontrollers (IC810). It runs from internal ROM and RAM, thus leaving
all four ports free for input/output functions.
Non-volatile data storage is achieved by serial communication with a 16kBit EEPROM
(IC820). This serial bus is also used by the microcontroller to program the synthesiser
(IC740) and deviation control EPOTS (IC220).
The main tasks of the microcontroller are as follows:
• program the synthesiser and EPOT;
• interface with the PGM800Win programming software at 9600 baud via the
serial communication lines on D-range 1 (PL100) & D-range 2;
• monitor channel change inputs from D-range 2;
• generate timing waveforms for CTCSS encoding;
• coordinate and implement timing control of the exciter/transmitter.
• control the front panel "Supply" LED.
10/07/00
5V Digital Watchdog
Regulator Reset
5V Reset
Microcontroller
CTCSS
Encoder
Figure 2.2 T881 Microcontroller Block Diagram
Microcontroller Cavity
Channel
Select
Port
Auxiliary
Output
Port
EEPROM
M880-00
Dual Digital
Potentiometer
Synthesiser
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