M3850 RENESAS [Renesas Technology Corp], M3850 Datasheet - Page 7

• Manufacturer Part Number: M3850
• Description: SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER
• Manufacturer: RENESAS [Renesas Technology Corp]

Fig. 5 740 Family CPU register structure
3850 Group (Spec.A)
FUNCTIONAL DESCRIPTION
CENTRAL PROCESSING UNIT (CPU)
The 3850 group (spec. A) uses the standard 740 Family instruc-
tion set. Refer to the table of 740 Family addressing modes and
machine instructions or the 740 Family Software Manual for de-
tails on the instruction set.
Machine-resident 740 Family instructions are as follows:
[Accumulator (A)]
The accumulator is an 8-bit register. Data operations such as data
transfer, etc., are executed mainly through the accumulator.
[Index Register X (X)]
The index register X is an 8-bit register. In the index addressing
modes, the value of the OPERAND is added to the contents of
register X and specifies the real address.
[Index Register Y (Y)]
The index register Y is an 8-bit register. In partial instruction, the
value of the OPERAND is added to the contents of register Y and
specifies the real address.
Rev.2.10
REJ03B0093-0210
The FST and SLW instructions cannot be used.
The STP, WIT, MUL, and DIV instructions can be used.
2005.11.14
b15
page 7 of 86
PC
H
b7
b7
b7
b7
b7
b7
N V T B D I Z C
PC
A
X
Y
S
L
b0
b0
b0
b0
b0
b0
[Stack Pointer (S)]
The stack pointer is an 8-bit register used during subroutine calls
and interrupts. This register indicates start address of stored area
(stack) for storing registers during subroutine calls and interrupts.
The low-order 8 bits of the stack address are determined by the
contents of the stack pointer. The high-order 8 bits of the stack ad-
dress are determined by the stack page selection bit. If the stack
page selection bit is “0” , the high-order 8 bits becomes “00
the stack page selection bit is “1”, the high-order 8 bits becomes
“01
The operations of pushing register contents onto the stack and
popping them from the stack are shown in Figure 6.
Store registers other than those described in Figure 6 with pro-
gram when the user needs them during interrupts or subroutine
calls.
[Program Counter (PC)]
The program counter is a 16-bit counter consisting of two 8-bit
registers PC
next instruction to be executed.
16
Accumulator
Index register X
Index register Y
Stack pointer
Program counter
Processor status register (PS)
Carry flag
Zero flag
Interrupt disable flag
Decimal mode flag
Break flag
Index X mode flag
Overflow flag
Negative flag
”.
H
and PC
L
. It is used to indicate the address of the
16
”. If