Oki 3321 Printer User Manual


 
2 – 3
(2) Program ROM
This is a 256 × 16 bits (4M bit) [MAX] EPROM with 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 signal of the MPU.
The following shows the operation of the memory access.
MPU CLOCK
A0~A17
PG-N
PSEN-N
D0~D15
Program Program Program
IN IN IN
CSO
PSEN
CE
OE
PG-N
D0~D15
A0~A17
MPU ROM