NB85E View Datasheet(PDF) - NEC => Renesas Technology
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NB85E Datasheet PDF : 226 Pages
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CHAPTER 2 REGISTER SET
2.2.4 Program status word (PSW)
The program status word (PSW) is a collection of flags that indicate the status of the program (result of instruction
execution) and the status of the CPU.
If the contents of the bits in this register are modified by the LDSR instruction, the PSW will assume the new value
immediately after the LDSR instruction has been executed. Setting the ID flag to 1, however, will disable interrupt
requests even while the LDSR instruction is being executed.
Bits 31 to 12 and 10 to 8 are reserved for future function expansion (fixed to 0).
Figure 2-6. Program Status Word (PSW) (1/2)
31
12 11 10 9 8 7 6 5 4 3 2 1 0
PSW
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
S
S
0
0
0
N
P
E
P
I
D
S
A
T
C
Y
O
V
S
Z Initial value
00000020H
Bit Position Flag Name
Function
11
SSNote
Operates with single-step execution when this flag is set to 1 (debug trap occurs each time
instruction is executed).
This flag is cleared to 0 when branching to the interrupt servicing routine.
When the SE bit of the DIR register is 0, this flag is not set (fixed to 0).
7
NP
Indicates that non-maskable interrupt (NMI) servicing is in progress. This flag is set to 1
when an NMI request is acknowledged, and multiple interrupt servicing is disabled.
0: NMI servicing is not in progress
1: NMI servicing is in progress
6
EP
Indicates that exception processing is in progress. This flag is set to 1 when an exception
occurs. Even when this bit is set, interrupt requests can be acknowledged.
0: Exception processing is not in progress
1: Exception processing is in progress
5
ID
Indicates whether a maskable interrupt request can be acknowledged.
0: Interrupts enabled (EI)
1: Interrupts disabled (DI)
4
SATNote
Indicates that an overflow has occurred in a saturated operation and the result is saturated.
This is a cumulative flag. When the result is saturated, the flag is set to 1 and is not cleared
to 0 even if the next result is not saturated. To clear this flag to 0, use the LDSR instruction.
This flag is neither set to 1 nor cleared to 0 by execution of an arithmetic operation
instruction.
0: Not saturated
1: Saturated
3
CY
Indicates whether a carry or borrow occurred as a result of the operation.
0: Carry or borrow did not occur
1: Carry or borrow occurred
2
OVNote
Indicates whether overflow occurred as a result of the operation.
0: Overflow did not occur
1: Overflow occurred
Note Can only be used in type A or B products. Cannot be used in other product types.
User’s Manual U14559EJ3V1UM
21
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