HD404328 Datasheet, PDF (15/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
Functional Description
Registers and Flags
The MCU has nine registers and two flags for CPU operations. They are shown in figure 5 and described
below.
Accumulator
Initial value: Undefined, R/W
3
0
(A)
B register
Initial value: Undefined, R/W
3
0
(B)
W register
Initial value: Undefined, R/W
10
(W)
X register
Initial value: Undefined, R/W
3
0
(X)
Y register
Initial value: Undefined, R/W
3
0
(Y)
SPX register
Initial value: Undefined, R/W
3
0
(SPX)
SPY register
Initial value: Undefined, R/W
3
0
(SPY)
Carry
Initial value: Undefined, R/W
0
(CA)
0
Status
Initial value: 1, no R/W
(ST)
Program counter
13
Initial value: 0,
no R/W
Stack pointer
Initial value: $3FF, no R/W
0
(PC)
9
5
0
1 11 1
(SP)
Figure 5 Registers and Flags
Accumulator (A), B Register (B): Four-bit registers used to hold results from the arithmetic logic unit
(ALU) and transfer data between memory, I/O, and other registers.
13