Circuit Blocks; Keypad Risc Processor; Memory; Memory Back-Up Circuit - Telstra Commander E105 Installation And Maintenance Manual

Microcomputer Unit
Circuit (Mhl Circuit)

Keypad RISC Processor

Memory

Memory Back-Up Circuit

Reset

Power Supply

Isolation Transformer

Refer to Illustration 6 - Keystation Circuit Block Diagram.
Controls keystation operation. The MCU works in conjunction with
other keystations (and the OFF&E, if installed) to control the system
operation.
Specifically, the keystation central microcomputer controls the:
.
exchange line interface
.
keystation communications and operation
.
intercom keystation interconnection
.
connection of signal tones to the keystation
.
system option programming.
This process or provides an intelligent interface between the keypad and
the station Microcontroller unit. It provides mapping for all 'intelligent
keys', such as DSS/Speed Dial keys and Centel@ functions keys.
Keystation memory consists of 8K words of ROM (10 bits per word)
and 5 12 words of RAM (4 bits per word).The microcomputer uses the
Random Access Memory (RAM) to store abbreviated dialling codes.
The microcomputer uses Read Only Memory (ROM) to store the
keystation's operating program.
During brief power down periods, the memory back-up circuitprotects
the abbreviated numbers stored in RAM. This circuit consists of a
supercapacitor (charged ready for use under normal keystation
operating conditions) and associated control circuitry.
When low voltages are detected, the reset circuit transmits an interrupt
signal to the Microcomputer Unit (MCU) and generates a reset pulse
when power is restored.
A DC-DC converter that steps down and isolates bus voltages to
supply the keystation circuit requirements.
Isolates keystation circuitry from the bus.