455A Datasheet, PDF (21/148 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

455A Group
PROGRAM MEMORY (ROM)
The program memory is a mask ROM. 1 word of ROM is
composed of 10 bits. ROM is separated every 128 words by the
unit of page (addresses 0 to 127). Table 8 shows the ROM size
and pages. Figure 21 shows the ROM map of M3455AGD.
A part of page 1 (addresses 008016 to 00FF16) is reserved for
interrupt addresses (Figure 22). When an interrupt occurs, the
address (interrupt address) corresponding to each interrupt is set
in the program counter, and the instruction at the interrupt
address is executed. When using an interrupt service routine,
write the instruction generating the branch to that routine at an
interrupt address.
Page 2 (addresses 010016 to 017F16) is the special page for
subroutine calls. Subroutines written in this page can be called
from any page with the 1-word instruction (BM). Subroutines
extending from page 2 to another page can also be called with the
BM instruction when it starts on page 2.
ROM pattern (bits 9 to 0) of all addresses can be used as data
areas with the TABP p instruction.
Table 8 ROM size and pages
Part number
ROM (PROM) size
(× 10 bits)
Pages
M3455AG8
8192 words
64 (0 to 63)
M3455AGC (Note 1) 12288 words
96 (0 to 95)
Note1.In the initial state, data in pages 0 to 63 can be
refered with the TABP instruction. Data in pages
64 to 95 can be refferd with the TABP p instruction
after the SBK instruction is executed.Data in
pages 0 to 63 can be referred with the TABP p
instruction after the RBK instruction is executed.
98 7 6 5 4 3 2 1
000016
007F16
008016
00FF16
010016
017F16
018016
Interrupt address page
Subroutine special page
0
Page 0
Page 1
Page 2
Page 3
2FFF16
Fig 21. ROM map of M3455AGC
Page 95
9876543210
008016 ^{External 0 interrupt address}
008216
008416
Timer 1 interrupt address
ROM Code Protect Address
When selecting the protect bit write by using a serial
programmer or selecting protect enabled for writing shipment by
Renesas Technology corp., reading or writing from/to QzROM is
disabled by a serial programmer.
As for the QzROM product in blank, the ROM code is protected
by selecting the protect bit write at ROM writing with a serial
programmer.
As for the QzROM product shipped after writing, whether the
ROM code protect is used or not can be selected as ROM option
setup (“MASK option” written in the mask file converter) when
ordering.
008616
008816
008A16
008C16
008E16
Timer 2 interrupt address
Timer 3 interrupt address
00FF16
Fig 22. Page 1 (addresses 008016 to 00FF16) structure
Rev.1.01 Feb 15, 2008 Page 21 of 146
REJ03B0224-0101