MB89051PFM View Datasheet(PDF) - 3M
Part Name
Description
MFG CO.
'MB89051PFM' PDF : 40 Pages View PDF
MB89051 Series
2. Registers
The MB89051 series has two types of registers; the registers dedicated to specific purposes in the CPU and
the general-purpose registers.
The dedicated registers are as follows:
Program counter (PC)
Accumulator (A)
Temporary accumulator (T)
Index register (IX)
Extra pointer (EP)
Stack pointer (SP)
Program status (PS)
: A 16-bit register to indicate locations where instructions are stored.
:
A 16-bit register for temporary storage of operations. In the case of an 8-bit
data processing instruction, the lower one byte is used.
:
A 16-bit register which performs operations with the accumulator.In the case of
an 8-bit data processing instruction, the lower one byte is used.
: A 16-bit register for index modification.
: A 16-bit register to point to a memory address.
: A 16-bit register to indicate a stack area.
: A 16-bit register to store a register pointer or a condition code.
16 bits
PC
A
T
IX
EP
SP
RP
CCR
PS
: Program counter
: Accumulator
: Temporary accumulator
: Index register
: Extra pointer
: Stack pointer
: Program status
Initial value
FFFDH
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
I-flag = 0, IL1, 0 = 11
Initial values for other bits are
indeterminate.
The PS register can further be divided into the register bank pointer in the higher 8 bits (RP) and the condition
code register in the lower 8 bits (CCR). (See the diagram below.)
RP
CCR
bit15 bit14 bit13 bit12 bit11 bit10 bit9 bit8 bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 CCR initial value
PS R4 R3 R2 R1 R0 − − − H I IL1 IL0 N Z V C X011XXXXB
H-flag
I-flag
IL 1,0
N-flag
Z-flag
V-flag
C-flag
X: Undefined
17
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