4509 Datasheet, PDF (18/142 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4509 Group
DATA MEMORY (RAM)
1 word of RAM is composed of 4 bits, but 1-bit manipulation (with
the SB j, RB j, and SZB j instructions) is enabled for the entire
memory area. A RAM address is specified by a data pointer. The
data pointer consists of registers Z, X, and Y. Set a value to the
data pointer certainly when executing an instruction to access
RAM.
Table 2 shows the RAM size. Figure 12 shows the RAM map.
• Note
Register Z of data pointer is undefined after system is released
from reset.
Also, registers Z, X and Y are undefined in the RAM back-up. After
system is returned from the RAM back-up, set these registers.
Table 2 RAM size
Part number
M34509G4
M34509G4H
RAM size
256 words ✕ 4 bits (1024 bits)
256 words ✕ 4 bits (1024 bits)
RAM 256 words ✕ 4 bits (1024 bits)
Register Z
0
Register X 0 1 2 3 ^... 6 7 ^........ 15
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Fig. 12 RAM map
Rev.1.02 2006.12.22 page 18 of 140
REJ03B0147-0102