Memory Space Expansion Features
21
Mitsubishi microcomputers
M16C / 62N Group
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
Memory Space Expansion Features
Here follows the description of the memory space expansion features.
With the processor running in memory expansion mode or in microprocessor mode, the memory space
expansion features provide the means of expanding the accessible space. The memory space expansion
features run in one of the three modes given below.
(1) Normal mode (no expansion)
(2) Memory space expansion mode (to be referred as expansion mode)
Use bits 5 and 4 (PM15, PM14) of processor mode register 1 to select a desired mode. The external
memory area the chip select signal indicates is different in mode so that the accessible memory space
varies. Table 1.7.1 shows how to set individual modes and corresponding accessible memory spaces. For
external memory area the chip select signal indicates, see Table 1.10.1 on page 31.
Table 1.7.1. The way of setting memory space expansion mode and corresponding memory space
Expansion mode
How to set PM15 and PM14
Accessible memory space
Normal mode (no expansion)
0, 0
Up to 1M byte
Expansion mode
1, 1
Up to 4M bytes
Here follows the description of individual modes.
(1) Normal mode (a mode with memory not expanded)
‘Normal mode’ means a mode in which memory is not expanded.
Figure 1.7.1 shows the memory maps and the chip select areas in normal mode.
Microprocessor mode
SFR area
Internal RAMarea
External area
Internal area reserved
0000016
0040016
XXXXX16
YYYYY16
FFFFF16
D000016
Note 1: These memory maps show an instance in which PM13 is set to 0; but in the case of products in which the internal
RAM and the internal ROM are expanded to over 15 Kbytes and 192 Kbytes, respectively, they show an instance
in which PM13 is set to 1.
Note 2: The memory maps in single-chip mode are omitted.
0800016
Memory expansion mode
SFR area
Internal RAM area
External area
Internal ROM area
Internal area reserved
CS3 (16K bytes)
CS2 (128K bytes)
CS1 (32K bytes)
CS0
Memory expansion mode: 640K bytes
Microprocessor mode: 832K bytes
2800016
3000016
0400016
Normal mode (memory area = 1M bytes for PM15 = 0, PM14 = 0)
Address YYYYY16
053FF16
Address XXXXX16
ROM size
02BFF16
10K bytes
20K bytes
RAM size
C000016
E000016
128K bytes
256K bytes
033FF16
12K bytes
Figure 1.7.1. The memory maps and the chip select areas in normal mode