CHAPTER 7 INTERRUPT/EXCEPTION PROCESSING FUNCTION
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User’s Manual U15195EJ5V0UD
7.3.6 In-service
priority register (ISPR)
This register holds the priority level of the maskable interrupt currently acknowledged. When an interrupt request is
acknowledged, the bit of this register corresponding to the priority level of that interrupt request is set to 1 and remains
set while the interrupt is serviced.
When the RETI instruction is executed, the bit corresponding to the interrupt request having the highest priority is
automatically cleared to 0 by hardware. However, it is not cleared to 0 when execution is returned from non-maskable
interrupt servicing or exception processing.
This register is read-only, in 8-bit or 1-bit units.
Caution In the interrupt enabled (EI) state, if an interrupt is acknowledged during the reading of the ISPR
register, the value of the ISPR register may be read after the bit is set (1) by this interrupt
acknowledgment. To read the value of the ISPR register properly before interrupt
acknowledgment, read it in the interrupt disabled (DI) state.
Address
FFFFF1FAH
<7>
ISPR7
ISPR
<6>
ISPR6
<5>
ISPR5
<4>
ISPR4
<3>
ISPR3
<2>
ISPR2
<1>
ISPR1
<0>
ISPR0
After reset
00H
Bit position
Bit name
Function
7 to 0
ISPR7 to ISPR0
Indicates priority of interrupt currently acknowledged
0: Interrupt request with priority n not acknowledged
1: Interrupt request with priority n acknowledged
Remark
n = 0 to 7 (priority level)