uPD780065 Subseries PUM - Renesas Electronics

21.1 Memory Size Switching Register
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CHAPTER 21 μPD78F0066
The μPD78F0066 allows users to select the internal memory capacity using the memory size switching register
(IMS) so that the same memory map as that of the μPD780065 with a different size of internal memory capacity can
be achieved.
IMS is set by using an 8-bit memory manipulation instruction.
RESET input sets IMS to CFH.
Caution The initial value of IMS is CFH (setting prohibited). As the initial program setting, be sure to
set the following values.
μPD780065: CAH
μPD78F0066: CCH or a value supporting the Mask ROM version
Address: FFF0H After reset: CFH R/W
Figure 21-1. Format of Memory Size Switching Register (IMS)
Symbol 7 6 5 4 3 2 1 0
IMS RAM2 RAM1 RAM0 0 ROM3 ROM2 ROM1 ROM0
RAM2 RAM1 RAM0 Internal high-speed RAM capacity selection
1 1 0 1024 bytes
Other than above Setting prohibited
ROM3 ROM2 ROM1 ROM0 Internal ROM capacity selection
1 0 1 0 40 Kbytes
1 1 0 0 48 Kbytes
Other than above Setting prohibited
Preliminary User’s Manual U13420EJ2V0UM00