CHAPTER 3 CPU ARCHITECTURE
User's Manual U11919EJ3V0UM00
46
3.1.1 Internal program memory space
The internal program memory space stores programs and table data. This space is usually addressed by the
program counter (PC).
The
µ
PD789026 Subseries provides the internal ROMs (or flash memory) containing the following capacities on
each product.
Table 3-1. Internal ROM Capacity
Internal ROM
Part Number
Structure
Capacity
µ
PD789022
4,096
×
8 bits
µ
PD789024
8,192
×
8 bits
µ
PD789025
12,288
×
8 bits
µ
PD789026
Mask ROM
16,384
×
8 bits
µ
PD78F9026A
Flash memory
16,384
×
8 bits
The following areas are allocated to the internal program memory space:
(1)
Vector table area
A 44-byte area of addresses 0000H to 002BH is reserved as a vector table area. This area stores program
start addresses to be used when branching by the RESET input or an interrupt request generation. Of a 16-
bit program address, the low-order 8 bits are stored in an even address, and the high-order 8 bits are stored
in an odd address.
Table 3-2. Vector Table
Vector Table Address
Interrupt Request
Vector Table Address
Interrupt Request
0000H
RESET input
000CH
INTSR/INTCSI0
0004H
INTWDT
000EH
INTST
0006H
INTP0
0010H
INTTM0
0008H
INTP1
0014H
INTTM2
000AH
INTP2
002AH
INTKR
(2)
CALLT instruction table area
In a 64-byte area of addresses 0040H to 007FH, the subroutine entry address of a 1-byte call instruction
(CALLT) can be stored.
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