Samsung ML-920 Service Manual page 141

CIRCUIT DESCRIPTION
3-2-4 PROGRAM ROM (FLASH MEMORY) CONTROL
1) DEVICE
TYPE No...................................AM29F800B
CAPACITY................................4 MBYTE (512K * 16BITS * 4)
2) PROGRAMMING
BEFORE ASS'Y.......................EPROM PROGRAMMER or PROGRAMMING at the factory
AFTER ASS'Y ..........................DOWNLOAD from PC
3) OPERATING PRINCIPLE
When the RCSO(ROM CHIP SELECT)signal is activated from the CPU after the POWER is ON, it activates RD SIGNAL
and reads the DATA(HIGH/LOW) stored in the FLASH MEMORY to control the overall system.
The FLASH MEMORY may also write. When turning the power on, press and hold the key(power switch) for 2 - 3 seconds,
then the LED will scroll and the PROGRAM DOWNLOAD MODE will be activated. In this mode, you can download the pro-
gram through the parallel port.
Tr Ta Tw Tw Tw Tw Tw Tw Tw Td Tr Tr Tr Tr
MCLK
nWR
A23-2
nROMCS
nTA
ACC+1
SETUP
HOLD
<Write Timing Diagram for Two Beat Burst Cycle>
Repair Manual
3-11
Samsung Electronics
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