MITSUBISHI MICROCOMPUTERS
M37754M8C-XXXGP, M37754M8C-XXXHP
M37754S4CGP, M37754S4CHP
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
In index addressing mode, register X is used as the index register
CENTRAL PROCESSING UNIT (CPU)
The CPU has ten registers and is shown in Figure 3. Each of these
registers is described below.
and the contents of this address is added to obtain the real address.
Index register X functions as a pointer register which indicates an
address of data table in instructions MVP, MVN, RMPA (Repeat
MultiPly and Accumulate).
ACCUMULATOR A (A)
Accumulator A is the main register of the microcomputer. It consists
of 16 bits and the low-order 8 bits can be used separately. The data
length flag m determines whether the register is used as 16-bit regis-
ter or as 8-bit register. It is used as a 16-bit register when flag m is “0”
and as an 8-bit register when flag m is “1”. Flag m is a part of the pro-
cessor status register (PS) which is described later.
INDEX REGISTER Y (Y)
Index register Y consists of 16 bits and the low-order 8 bits can be
used separately. The index register length flag x determines whether
the register is used as 16-bit register or as 8-bit register. It is used as
a 16-bit register when flag x is “0” and as an 8-bit register when flag x
is “1”. Flag x is a part of the processor status register (PS) which is
described later.
Data operations such as calculations, data transfer, input/output,
etc., is executed mainly through the accumulator.
In index addressing mode, register Y is used as the index register
and the contents of this address is added to obtain the real address.
Index register Y functions as a pointer register which indicates an
address of data table in instructions MVP, MVN, RMPA (Repeat
MultiPly and Accumulate).
ACCUMULATOR B (B)
Accumulator B has the same functions as accumulator A, but the use
of accumulator B requires more instruction bytes and execution
cycles than accumulator A.
INDEX REGISTER X (X)
Index register X consists of 16 bits and the low-order 8 bits can be
used separately. The index register length flag x determines whether
the register is used as 16-bit register or as 8-bit register. It is used as
a 16-bit register when flag x is “0” and as an 8-bit register when flag
x is “1”. Flag x is a part of the processor status register (PS) which is
described later.
15
7
7
0
0
0
0
0
0
0
0
AH
AL
BL
XL
YL
Accumulator A
15
15
15
15
15
15
BH
XH
YH
Accumulator B
7
7
Index register X
Index register Y
7
7
0
0
S
Stack pointer S
PG
DT
Program bank register PG
Data bank register DT
PC
Program counter PC
Direct page register DPR
Processor status register PS
DPR
7
15
0
IPL2 IPL1 IPL0
0
0
0
0
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 IPL
Fig. 3 Register structure
9
RENESAS [ RENESAS TECHNOLOGY CORP ]
