M37754 Mitsubishi, M37754 Datasheet - Page 9

• Manufacturer Part Number: M37754
• Description: SINGLE-CHIP 16BIT CMOS MICROCOMPUTER
• Manufacturer: Mitsubishi

CENTRAL PROCESSING UNIT (CPU)
The CPU has ten registers and is shown in Figure 3. Each of these
registers is described below.
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.
Data operations such as calculations, data transfer, input/output,
etc., is executed mainly through the accumulator.
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.
Fig. 3 Register structure
7
7
PG
DT
0
0
Program bank register PG
Data bank register DT
M37754M8C-XXXGP, M37754M8C-XXXHP
15
15
15
15
15
15
15
15
0 0 0 0 0
A
B
X
Y
H
H
H
H
IPL
2
IPL
In index addressing mode, register X is used as the index register
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).
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.
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).
1
M37754S4CGP, M37754S4CHP
IPL
DPR
PC
0
S
7
7
7
7
N V m x D I
7
SINGLE-CHIP 16-BIT CMOS MICROCOMPUTER
A
B
X
Y
L
L
L
L
MITSUBISHI MICROCOMPUTERS
Z C
0
0
0
0
0
0
0
0
Accumulator A
Accumulator B
Index register X
Index register Y
Stack pointer S
Program counter PC
Direct page register DPR
Processor status register PS
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
9