CHAPTER 5 INTERRUPT/EXCEPTION PROCESSING FUNCTION
User’s Manual U13850EJ4V0UM
142
5.3.5 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 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 reset to 0 by hardware. However, it is not reset when execution is returned from non-maskable
processing or exception processing.
This register can be only read in 8- or 1-bit units.
Figure 5-12. In-Service Priority Register (ISPR) Format
After reset: 00H
R
Address: FFFFF166H
Symbol
<7>
<6>
<5>
<4>
<3>
<2>
<1>
<0>
ISPR
ISPR7
ISPR6
ISPR5
ISPR4
ISPR3
ISPR2
ISPR1
ISPR0
ISPRn
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)
5.3.6 Maskable interrupt status flag
The interrupt disable status flag (ID) of the PSW controls the enabling and disabling of maskable interrupt
requests. As a status flag, it also displays the current maskable interrupt acknowledgment condition.
Figure 5-13. Interrupt Disable Flag (ID)
After reset: 00000020H
Symbol
31
8
7
6
5
4
3
2
1
0
PSW
0
NP EP
ID
SAT CY OV S
Z
ID
Specifies maskable interrupt servicing
Note
0
Maskable interrupt acknowledgement enabled
1
Maskable interrupt acknowledgement disabled (pending)
Note
Interrupt disable flag (ID) function
It is set to 1 by the DI instruction and reset to 0 by the EI instruction. Its value is also modified by the RETI
instruction or LDSR instruction when referencing the PSW.
Non-maskable interrupt and exceptions are acknowledged regardless of this flag. When a maskable
interrupt is acknowledged, the ID flag is automatically set to 1 by hardware.
The interrupt request generated during the acknowledgement disabled period (ID = 1) can be
acknowledged when the xxIFn bit of xxICn is set to 1, and the ID flag is reset to 0.
Содержание MPD703030A
Страница 2: ...User s Manual U13850EJ4V0UM 2 MEMO ...
Страница 514: ...User s Manual U13850EJ4V0UM 514 MEMO ...