CENTRAL PROCESSING UNIT (CPU)
2.1 Central processing unit (CPU)
2.1 Central processing unit (CPU)
The CPU (Central Processing Unit) has 13 registers shown in Figure 2.1.1.
b8 b7
b0
b15
Accumulator A (A)
Accumulator B (B)
Accumulator E (E)
Index register X (X)
Index register Y (Y)
Stack pointer (S)
A
H
A
L
b8 b7
b0
b15
b31
BH
B
L
b0
b0
b0
b0
E
b8 b7
b8 b7
b8 b7
b15
b15
b15
XH
YH
SH
X
Y
S
L
L
L
b7
b0
Data bank register (DT)
DT
PG
b23
b16 b15
b8 b7
b0
Program counter (PC)
PC
H
PC
L
b7
b0
Program bank register (PG)
b15
b8 b7
b8 b7
b8 b7
b8 b7
b8 b7
b0
b0
b0
b0
b0
Direct page register 0 (DPR0)
Direct page register 1 (DPR1)
Direct page register 2 (DPR2)
Direct page register 3 (DPR3)
Processor status register (PS)
DPR0
H
H
H
H
DPR0
DPR1
DPR2
DPR3
L
L
L
L
b15
DPR1
b15
DPR2
b15
DPR3
b15
PS
H
PS
L
b15
b10
b8 b7 b6 b5 b4 b3 b2 b1 b0
0
0
0
0
0
IPL
N
V
m
x
D
I
Z
C
Carry flag
Zero flag
Interrupt disable flag
Decimal mode flag
Index register length flag
Data length flag
Overflow flag
Negative flag
Processor interrupt priority level
Fig. 2.1.1 CPU registers
7905 Group User’s Manual Rev.1.0
2-2
RENESAS [ RENESAS TECHNOLOGY CORP ]
