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LST
Load Status Register
7-88
Figure 7–4. LST #1 Operation
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ST0 ARP
OV OVM 1 INTM DP
↑ ↑ ↑
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Data
↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓ ↓
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ST1 ARB
CNF TC SXM C 1 1 1 1 XF 1 1 PM
Status Bits
Affects
ARB, ARP, OV, OVM, DP, CNF, TC, SXM, C, XF, and PM
This instruction does not affect INTM.
Description The specified status register (ST0 or ST1) is loaded with the addressed data-
memory value. Note the following points:
The LST #0 operation does not affect the ARB field in the ST1 register,
even though a new ARP is loaded.
During the LST #1 operation, the value loaded into ARB is also loaded into
ARP.
If a next AR value is specified as an operand in the indirect addressing
mode, this operand is ignored. ARP is loaded with the three MSBs of the
value contained in the addressed data-memory location.
Reserved bit values in the status registers are always read as 1s. Writes
to these bits have no effect.
The LST instruction can be used for restoring the status registers after subrou-
tine calls and interrupts.
Words 1
Cycles for a Single LST Instruction
Program
Operand ROM DARAM SARAM External
DARAM 2 2 2 2+p
code
SARAM 2 2 2, 3
†
2+p
code
External 2+d
src
2+d
src
2+d
src
3+d
src
+p
code
†
If the operand and the code are in the same SARAM block
Cycles