RL78/G10 CHAPTER 3 CPU ARCHITECTURE
R01UH0384EJ0311 Rev. 3.11 34
Dec 22, 2016
3.2.2 General-purpose registers
The general-purpose registers are a bank of eight 8-bit registers (X, A, C, B, E, D, L, and H) mapped to addresses
(FFEF8H to FFEFFH) of the data memory.
Each register can be used as an 8-bit register, and two 8-bit registers can also be used in a pair as a 16-bit register (AX,
BC, DE, and HL).
These registers can be described in terms of function names (X, A, C, B, E, D, L, H, AX, BC, DE, and HL) and absolute
names (R0 to R7 and RP0 to RP3).
Caution It is prohibited to use the general-purpose register (FFEF8H to FFEFFH) space for fetching
instructions or as a stack area.
Figure 3-8. Configuration of General-Purpose Registers
(a) Function name
General-purpose
register
FFEFFH
FFEF8H
HL
DE
BC
AX
H
15 0 7 0
L
D
E
B
C
A
X
16-bit processing
8-bit processing
(b) Absolute name
FFEFFH
FFEF8H
RP3
RP2
RP1
RP0
R7
15 0 7 0
R6
R5
R4
R3
R2
R1
R0
16-bit processing
8-bit processing
General-purpose
register
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