CHAPTER 3 CPU ARCHITECTURE
User’s Manual U15075EJ1V0UM00
53
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
PD789426, 789436, 789446, and 789456 Subseries provide internal ROM (or flash memory) with the
following capacity for each product.
Table 3-1. Internal ROM Capacity
Part Number
Internal ROM
Structure
Capacity
µ
PD789425, 789435,
789445, 789455
12288
×
8 bits
µ
PD789426, 789436,
789446, 789456
Mask ROM
16384
×
8 bits
µ
PD78F9436, 78F9456
Flash memory
16384
×
8 bits
The following areas are allocated to the internal program memory space.
(1)
Vector table area
The 34-byte area of addresses 0000H to 0021H 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 lower 8 bits are stored in an even address, and the higher 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
0014H
INTWTI
0004H
INTWDT
0016H
INTTM90
0006H
INTP0
0018H
INTTM50
0008H
INTP1
001AH
INTTM60
000AH
INTP2
001CH
INTAD0
000CH
INTP3
001EH
INTWT
000EH
INTSR20/INTCSI20
0020H
INTKR00
0012H
INTST20
(2)
CALLT instruction table area
The subroutine entry address of a 1-byte call instruction (CALLT) can be stored in the 64-byte area of
addresses 0040H to 007FH.
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