Ram / Rom Bank Selection Circuit - Casio CE-300 (EX-247) Service Manual

4-7. RAM / ROM bank selection circuit

This circuit is used for address decoder for memory.
0000
Mask ROM
(16 K)
2000
4000
EP ROM
Common (16 K)
6000
8000
EP ROM
Bank select area
A000
(16 K)
C000
RAM common area
(8 K)
E000
RAM BANK select
area (4 K)
F000
Outer I/O area
FA80
Internal RAM
(High speed access)
FFFF
Memory Map
00001
000000
Bank
0
— 9 —
RAM 256 K
00011 00101
00100
00010
Bank Bank Bank Bank
1 2 3 4
KI signal port (F800,F801)
Buffer RAM 32 bytes
Internal RAM
(High speed access)
288 bytes
Internal RAM
(High speed access)
Short direct area
192 bytes
General purpose
register 32 bytes
Special function
register (SFR)
256 bytes
RAM 1 M
11101
00110
Bank
Bank
29
5
F800
FAC0
FAE0
FD00
FE20
FEE0
FFF0