Internal Program Memory Space - NEC mPD789426 Series User Manual

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.
µ PD78F9436, 78F9456
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.
Vector Table Address
0000H
0004H
0006H
0008H
000AH
000CH
000EH
0012H
(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.
CHAPTER 3 CPU ARCHITECTURE
Table 3-1. Internal ROM Capacity
Part Number
µ PD789425, 789435,
789445, 789455
µ PD789426, 789436,
789446, 789456
Table 3-2. Vector Table
Interrupt Request
RESET input
INTWDT
INTP0
INTP1
INTP2
INTP3
INTSR20/INTCSI20
INTST20
User's Manual U15075EJ1V0UM00
Internal ROM
Structure
Mask ROM
Flash memory
Vector Table Address
0014H
0016H
0018H
001AH
001CH
001EH
0020H
Capacity
12288 × 8 bits
16384 × 8 bits
16384 × 8 bits
Interrupt Request
INTWTI
INTTM90
INTTM50
INTTM60
INTAD0
INTWT
INTKR00
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