MB89160/160A Series
2. Registers
The F2MC-8L family has two types of registers; dedicated registers in the CPU and general-purpose registers
in the memory. The following dedicated registers are provided:
Program counter (PC):
Accumulator (A):
A 16-bit register for indicating instruction storage positions
A 16-bit temporary register for storing arithmetic operations, etc. When the
instruction is an 8-bit data processing instruction, the lower byte is used.
Temporary accumulator (T): A 16-bit register which performs arithmetic operations with the accumulator
When the instruction is an 18-bit data processing instruction, the lower byte is used.
Index register (IX):
Extra pointer (EP):
Stack pointer (SP):
Program status (PS):
A 16-bit register for index modification
A 16-bit pointer for indicating a memory address
A 16-bit register for indicating a stack area
A 16-bit register for storing a register pointer, a condition code
Initial value
16 bits
PC
A
: Program counter
: Accumulator
FFFDH
Undefined
Undefined
Undefined
Undefined
Undefined
T
: Temporary accumulator
: Index register
IX
EP
SP
PS
: Extra pointer
: Stack pointer
: Program status
I-flag = 0, IL1, 0 = 11
Other bits are undefined.
The PS can further be divide into higher 8 bits for use as a register bank pointer (RP) and the lower 8 bits for
use as a condition code register (CCR). (See the diagram below.)
Structure of the Program Status Register
15
14
13
12
11
10
9
8
7
6
I
5
4
3
2
Z
1
0
Vacancy
Vacancy
PS
RP
Vacancy
H
IL1, 0
N
V
C
RP
CCR
23
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