Oki ML63326, User Manual, Page: 43 / 322

2-4
ML63326 User's Manual
Chapter 2 CPU and Memory Spaces
2.2.5 Program Counter (PC)
The program counter (PC) is a counter with 16 valid bits that specifies the program memory
space.
2.2.6 RA Registers (RA3, RA2, RA1, RA0)
The RA registers are used for indirect program memory addressing (ROM table reference
instructions).
Figure 2-2 shows the address configuration of the RA registers.
At system reset, RA3 to RA0 are initialized to "0".
!
Note:
When executing a ROM table reference instruction that uses RA registers, do not use
addresses located in the SFR area to transfer ROM table data to RA registers, otherwise
indirect addressing of program memory will not operate properly.
RA3 RA2 RA1 RA0
A15–A12 A11–A8 A7–A4 A3–A0
Figure 2-2 Address Configuration of RA3 to RA0 Registers
Within the A15 to A0 of Figure 2-2, A14 to A0 indicate program memory addresses (32K
words max.).
RA3 to RA0 are assigned to special function register (SFR) addresses 0F2H to 0F5H.
a
15
a
14
a
13
a
12
RA3
bit 3 bit 2 bit 1 bit 0
a
11
a
10
a
9
a
8
RA2
bit 3 bit 2 bit 1 bit 0
RA1
bit 3 bit 2 bit 1 bit 0
RA0
bit 3 bit 2 bit 1 bit 0
a
7
a
6
a
5
a
4
a
3
a
2
a
1
a
0
(0F5H)
(R/W)
(0F4H)
(R/W)
(0F3H)
(R/W)
(0F2H)
(R/W)