uPD789871 Subseries 8-Bit Single-Chip Microcontrollers PUM

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CHAPTER 3 CPU ARCHITECTURE
3.2.2 General-purpose registers
The general-purpose registers consist of eight 8-bit registers (X, A, C, B, E, D, L, and H).
Each register can be used as an 8-bit register, and in addition, two 8-bit registers in pairs can be used as a 16bit
register (AX, BC, DE, and HL).
They can be described in terms of functional names (X, A, C, B, E, D, L, H, AX, BC, DE, and HL) and absolute
names (R0 to R7 and RP0 to RP3).
Figure 3-12. General-Purpose Register Configuration
(a) Absolute names
16-bit processing 8-bit processing
RP3
RP2
RP1
RP0
15 0 7 0
(b) Functional names
16-bit processing 8-bit processing
HL
DE
BC
AX
15 0 7 0
Preliminary User’s Manual U14938EJ1V0UM
R7
R6
R5
R4
R3
R2
R1
R0
H
L
D
E
B
C
A
X