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SH69P55A/K55A
11
3. ROM
The ROM can address 8192 X 16 bits of program area from $000 to $1FFF.
3.1. Vector Address Area ($000 to $004)
The program is sequentially executed. There is an area address $000 through $004 that is reserved for a special interrupt
service routine such as starting vector address.
Address Instruction
Remarks
$000
JMP*
Jump to RESET service routine
$001
JMP*
Jump to TIMER0 interrupt service routine
$002
JMP*
Jump to TIMER1 interrupt service routine
$003
JMP*
Jump to TIMER2 interrupt service routine
$004
JMP*
Jump to External interrupts service routine
* JMP instruction can be replaced by any instruction.
3.2. Bank Switch Mapping
Program Counter (PC11 - PC0) can only address 4K ROM Space. The bank switch technique is used to extend the CPU
address space. The lower 2K of the CPU address space maps to the lower 2K of ROM space (BANK0). The upper 2K of the
CPU address space maps to one of the three banks (BNK3-0 = 0, 1, 2) of the upper 6K of ROM.
The bank switch mapping is as follows:
ROM Space
CPU Address
BNK = $00
BNK = $01
BNK = $02
Low 2K address
0000 - 07FF
(BANK 0)
0000 - 07FF
(BANK 0)
0000 - 07FF
(BANK 0)
Upper 2K address
0800 - 0FFF
(BANK 1)
1000 - 17FF
(BANK 2)
1800 - 1FFF
(BANK 3)