Memory Size Switching Register; Examples Of Memory Size Switching Register Settings; Memory Size Switching Register Format - NEC PD78081(A) User Manual

15.1 Memory Size Switching Register

It is possible to specify the internal memory of the 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 PD78081 and 78082,
which have different internal memory.
IMS is set with an 8-bit memory manipulation instruction.
RESET input sets IMS to 46H.
Symbol 7 6
IMS RAM2 RAM1 RAM0
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
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CHAPTER 15
Figure 15-1. Memory Size Switching Register Format
5 4 3 2 1
0 ROM3 ROM2 ROM1
Relevant Mask ROM Version
PD78081
PD78082
PD78P083
After
Address
0
Reset
FFF0H 46H
ROM0
ROM3 ROM2 ROM1 ROM0
0 0 1
0 1 0
0 1 1
Other than above
RAM2 RAM1 RAM0 Internal High-Speed RAM Capacity Selection
0 1 0
0 1 1
1 0 0
Other than above
IMS Setting
82H
64H
R/W
R/W
Internal ROM Capacity Selection
0 8 Kbytes
0 16 Kbytes
0 24 Kbytes
Setting prohibited
512 bytes
384 bytes
256 bytes
Setting prohibited