UPD784026 Renesas Electronics Corporation., UPD784026 Datasheet - Page 562

• Manufacturer Part Number: UPD784026
• Description: 16/8-bit Single-chip Microcontrollers
• Manufacturer: Renesas Electronics Corporation.

20.7.3 Maskable Interrupt Priority Levels
another interrupt. Nesting interrupts can be controlled by priority levels.
the setting of the priority specification flag. In priority control by means of default priority, interrupt processing is performed
in accordance with the priority preassigned to each interrupt request (default priority) (see Table 20-2). In programmable
priority control, interrupt requests are divided into four levels according to the setting of the priority specification flag. Interrupt
requests for which nesting interrupt is permitted are shown in Table 20-5.
flag should be set (1) to enable interrupts by executing an EI instruction in the interrupt service program, etc.
522
No interrupt being
acknowledged
3
2
1
0
Non-maskable interrupts
Priority of Interrupt Currently
The PD784026 performs nesting interrupt processing in which an interrupt is acknowledged during processing of
There are two kinds of priority control, control by default priority and programmable priority control in accordance with
Since the IE flag is cleared (0) automatically when an interrupt is acknowledged, when nesting interrupt is used, the IE
Being Acknowledged
ISPR Value
00000000
00001000
0000 100
0000
0000
1000
0100
1100
10
1
CHAPTER 20 INTERRUPT FUNCTIONS
Table 20-5 Nesting Interrupt
IE Flag in PSW
0
1
0
1
1
0
1
0
1
IMC Register
PRSL in
0
1
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Acknowledgeable Maskable Interrupts
All macro service only
All maskable interrupts
All macro service only
All maskable interrupts
All macro service
Maskable interrupts specified as
priority 0/1/2
All macro service only
All macro service
Maskable interrupts specified as
priority 0/1
All macro service only
All macro service
Maskable interrupts specified as
priority 0
All macro service only
All macro service only