CHAPTER 3 CPU ARCHITECTURE
User’s Manual U15075EJ2V1UD
52
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.
Содержание UPD789426 Series
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