Internal Memory Size Switching Register; Format Of Internal Memory Size Switching Register (Ims) - NEC 78K0 User Manual

28.1 Internal Memory Size Switching Register

µ
The PD78F0148 allows users to select the internal memory capacity using the internal memory size switching
register (IMS) so that the same memory map as that of the mask ROM versions with a different internal memory
capacity can be achieved.
IMS is set by an 8-bit memory manipulation instruction.
RESET input sets IMS to CFH.
Caution Be sure to set the value of the relevant mask ROM version at initialization.
Figure 28-1. Format of Internal Memory Size Switching Register (IMS)
Address: FFF0H After reset: CFH
Symbol 7
IMS RAM2
RAM2
1
ROM3
0
1
1
1
The IMS settings required to obtain the same memory map as mask ROM versions are shown in Table 28-2.
Table 28-2. Internal Memory Size Switching Register Settings
Caution When using a mask ROM version, be sure to set the value indicated in Table 28-2 to IMS.
496
CHAPTER 28
R/W
6 5
RAM1 RAM0
RAM1 RAM0
1 0 1024 bytes
Other than above Setting prohibited
ROM2 ROM1
1 1
0 0
1 0
1 1
Other than above
Target Mask ROM Versions
µ
PD780143
µ
PD780144
µ
PD780146
µ
PD780148
User's Manual U15947EJ2V0UD
µ
PD78F0148
4 3 2
0 ROM3 ROM2
Internal high-speed RAM capacity selection
ROM0 Internal ROM capacity selection
0 24 KB
0 32 KB
*
0 48 KB
1 60 KB
Setting prohibited
IMS Setting
C6H
C8H
CCH
CFH
1 0
ROM1 ROM0