4571 Datasheet, PDF (16/126 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4571 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 (also, set a value after system returns from RAM
back-up).
Table 9 shows the RAM size. Figure 18 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 9 RAM size and pages
Part number
M34571G4
M34571G6
M34571GD
RAM size
128 words × 4 bits (512 bits)
RAM 128 words × 4 bits (512 bits)
Register Z
0
Register X 0 1 2 3 ^... 6 7
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Z=0
X=0 to 7
Y=0 to 15
128 words × 4 bits (512 bits)
M34571G4
M34571G6
M34571GD
Fig 18. RAM map
Rev.1.02 May 25, 2007 Page 16 of 124
REJ03B0179-0102