Oki ML490 Maintenance Manual page 11

(2) Program ROM
This is a 512K
program for the printer stored. The MPU executes instructions under this program.
The program ROM is assigned to the program memory area of the MPU and is fetched
by the PSEN-N signal of the MPU.
The following shows the operation of the memory access.
42114101 Rev.1
16 bits (8M bit) [MAX 16M bit] OTPROM or MASK ROM with the control
MPU
A0~A18
D0~D15
PG-N
CSO
PSEN-N
PSEN
MPU CLOCK
A0~A18
PG-N
PSEN-N
D0~D15
Program ROM
CE
OE
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