4554 Datasheet, PDF (21/138 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4554 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).
RAM includes the area for LCD.
When writing “1” to a bit corresponding to displayed segment, the
segment is turned on.
Table 2 shows the RAM size. Figure 12 shows the RAM map.
Table 2 RAM size
Part number
M34554M8
M34554MC
M34554ED
RAM size
512 words ✕ 4 bits (2048 bits)
512 words ✕ 4 bits (2048 bits)
512 words ✕ 4 bits (2048 bits)
• 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.
RAM 512 words ✕ 4 bits (2048 bits)
Register Z
0
1
Register X _{0 1} 2 3 ^... 12 ₁₃ 14 15 0 1 2 ^... 11 12 13 14 15
0
1
2
3
4
5
6
7
8
0 8 ¹⁶ 24
9
1 ^{9 17} 25
10
2 _{10 18 26}
11
3 11 19 ₂₇
12
4 12 _{20 28}
13
5 13 21 29
14
6 14 _{22 30}
15
7 15 23 31
Note: The numbers in the shaded area indicate the corresponding segment output pin numbers.
Fig. 12 RAM map
Rev.3.00 Aug 06, 2004 page 21 of 136
REJ03B0043-0300Z