Main Control Board (Mcnt-150) - OKIDATA OF1000 Service Manual

Page: 194
Service Guide OF1000
Chapter A Reference Charts
A.2.01 Main Control Board (MCNT-150)
Function
The MCNT-150 controls the speaker, converts parallel send data to serial data, converts serial
receive data to parallel data, modulates / demodulates data, and generates Multi-Frequency
signals for tone dialing. The board contains a 3-volt, non-rechargeable lithium battery, which
supplies voltage to the static RAM and real time clock circuit (month, day, year) whenever the unit
is powered OFF. IC22 provides voice answering in Tel/Fax Mode, in accordance with signals
received from the input / output gate array IC21 and the microprocessor IC1. VR1 is used for
modem voltage control, which is set at the factory. This board contains a modem IC. A 256K
P-RAM is used for memory broadcast, delayed broadcast, and ECM operation.
Firmware
· IC1 : 256 Kbyte ROM - Contains main control program
Fuses
NONE
Jumpers
NONE
Sensors
NONE
Switches
NONE
Test Points
CN7, Pins 08, 09, 10 : +5 vdc
CN7, Pins 01, 02 : +12 vdc
CN7, Pins 03, 04 : -12 vdc