Oki ML421 Maintenance Manual - Page 11
Program ROM
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Oki Data CONFIDENTIAL (2) Program ROM This is a 256 × 16 bits (4M bit) EPROM or MASK ROMwith the control 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. MPU CSO PSEN A0~A17 D0~D15 PG-N PSEN-N ROM CE OE MPU CLOCK A0~A17 PG-N PSEN-N D0~D15 42113901 Rev.2 11 /
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42113901
Rev.2
11 /
Oki
Data
CONFIDENTIAL
MPU CLOCK
A0~A17
PG-N
PSEN-N
D0~D15
CSO
PSEN
CE
OE
PG-N
PSEN-N
D0~D15
A0~A17
MPU
ROM
(2)
Program ROM
This is a 256
×
16 bits (4M bit) EPROM or MASK ROMwith the control 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.