UPD78320 Datasheet, PDF (24/88 Pages) NEC – 16/8-BIT SINGLE-CHIP MICROCONTROLLER

µPD78320, 78322
The sixteen 8-bit registers can function as eight 16-bit register pairs (RP0 to RP7) as well.
As shown in Table 2-1, the sixteen 8-bit registers are characterized by functional names. The X register functions as
the lower half of the 16-bit accumulator, the A register functions as the upper half of the 8-bit or 16-bit accumulator, the B
and C registers function as counters, and DE, HL, VP and UP function as address register pairs. In particular the VP register
functions as a base register and the UP register functions as a user stack pointer.
The unique function register changes as shown in Table 2-1 according to the value of the register set select flag (RSS)
in the PSW.
Thus, if the program is described by the functional name, another register set of X, A, C and B can be used by means
of the RSS flag.
The µPD78322 can carry out processed data addressing operations, implied addressing by functional names with
importance attached to the unique function of each register and register addressing by absolute names with a view to fast
processing with a small number of data transfers or creating highly descriptive programs.
Table 2-1. General Register Configuration
Absolute
Name
R0
R1
R2
R3
R4
R5
R6
R7
R8
R9
R10
R11
R12
R13
R14
R15
Functional Name
RSS = 0
RSS = 1
X
A
C
B
X
A
C
B
VPL
VPL
VPH
VPH
UPL
UPL
UPH
UPH
E
E
D
D
L
L
H
H
Absolute
Name
RP0
RP1
RP2
RP3
RP4
RP5
RP6
RP7
Functional Name
RSS = 0
RSS = 1
AX
BC
AX
BC
VP
VP
UP
UP
DE
DE
HL
HL
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