UPD784938 Datasheet, PDF (92/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 3 CPU ARCHITECTURE
3.8 General- Purpose Registers
3.8.1 Configuration
There are sixteen 8-bit general-purpose registers, and two 8-bit general-purpose registers can be used together as a 16-bit
general-purpose register. In addition, four of the 16-bit general-purpose registers can be combined with an 8-bit register for
address extension, and used as 24-bit address specification registers.
General-purpose registers other than the V, U, T, and W registers for address extension are mapped onto internal RAM.
These register sets are provided in 8 banks, and can be switched by means of software or the context switching function.
Upon RESET input, register bank 0 is selected. The register bank used during program execution can be checked by reading
the register bank selection flag (RBS0, RBS1, RBS2) in the PSW.
Figure 3-12. General-Purpose Register Format
7
07
0
A (R1)
X (R0)
AX (RP0)
B (R3)
C (R2)
BC (RP1)
R5
R4
RP2
R7
R6
RP3
V
R9
R8
VVP (RG4)
VP (RP4)
U
R11
R10
UUP (RG5)
UP (RP5)
T
D (R13)
E (R12)
TDE (RG6)
DE (RP6)
W
H (R15)
L (R14)
WHL (RG7)
HL (RP7)
23
15
0
Remark Absolute names are shown in parentheses.
8 banks
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Preliminary User’s Manual U13987EJ1V0UM00