CHAPTER 8 INTC
Preliminary User’s Manual A14874EJ3V0UM
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(3) In-service priority register (ISPR)
This register maintains the priority level of the maskable interrupt that is being acknowledged. When an interrupt
request is acknowledged, the bit corresponding to the priority level of that interrupt request is set (1) and
maintained while the interrupt is being serviced.
When the RETI instruction is executed, the bit corresponding to the interrupt request having the highest priority
among the bits that are set (1) within the ISPR register is automatically cleared (0). However, it is not cleared (0)
when control returns from non-maskable interrupt service or exception processing.
This register is read-only in 8-bit or 1-bit units.
Figure 8-10. In-Service Priority Register (ISPR)
7
6
5
4
3
2
1
0
ISPR
ISPR7
ISPR6
ISPR5
ISPR4
ISPR3
ISPR2
ISPR1
ISPR0
Address
FFFFF1FAH
After reset
00H
Bit position
Bit name
Function
7 to 0
ISPR7 to
ISPR0
Indicates the priority of the interrupt that is being acknowledged.
0: Interrupt request having priority n has not been acknowledged
1: Interrupt request having priority n is being acknowledged
Remark
n = 7 to 0 (priority levels)