NEC NEC PD78081(A), User Manual

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CHAPTER 15
µ
PD78P083
Caution If using mask ROM versions, do not specify any values in the IMS other than when resetting.
The IMS settings to give the same memory map as mask ROM versions are shown in Table 15-2.
Table 15-2. Examples of Memory Size Switching Register Settings
Relevant Mask ROM Version IMS Setting
µ
PD78081 82H
µ
PD78082 64H
15.1 Memory Size Switching Register
It is possible to specify the internal memory of the
µ
PD78P083 by means of the memory size switching register
(IMS). By setting the IMS, memory mapping can be made to match the memory mapping of the
µ
PD78081 and 78082,
which have different internal memory.
IMS is set with an 8-bit memory manipulation instruction.
RESET input sets IMS to 46H.
Figure 15-1. Memory Size Switching Register Format
7
RAM2
Symbol
IMS
6
RAM1
5
RAM0
4
0
3
ROM3
2
ROM2
1
ROM1
0
ROM0
Address
FFF0H 46H
After
Reset
R/W
R/W
0
Internal ROM Capacity Selection
24 Kbytes
ROM3
1
ROM2
1
ROM1
0
ROM0
Setting prohibited Other than above
Internal High-Speed RAM Capacity Selection RAM2 RAM1 RAM0
512 bytes 0 1 0
0
0
8 Kbytes
16 Kbytes
0
1
1
0
0
0
384 bytes 0 1 1
Setting prohibited Other than above
256 bytes 1 0 0