ST92196A STMicroelectronics, ST92196A Datasheet - Page 47

• Manufacturer Part Number: ST92196A
• Description: 8/16-bit Mcu For Tv Applications With Up To 96k Rom, On-screen-display And 1 Or 2 Data Slicers
• Manufacturer: STMicroelectronics

ARBITRATION MODES (Cont’d)
Examples
In the following two examples, three interrupt re-
quests with different priority levels (2, 3 & 4) occur
simultaneously during the interrupt 5 service rou-
tine.
Figure 19. Simple Example of a Sequence of Interrupt Requests with:
- Concurrent mode selected and
- IEN unchanged by the interrupt routines
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INTERRUPTS
0
1
2
3
4
5
6
7
CPL is set to 7
Priority Level of
Interrupt Request
MAIN
INT 5
ei
CPL = 7
INT 5
INT 2
INT 3
INT 4
CPL = 7
INT 2
CPL = 7
INT 3
CPL = 7
Example 1
In the first example, (simplest case,
ei instruction is not used within the interrupt serv-
ice routines. This means that no new interrupt can
be serviced in the middle of the current one. The
interrupt routines will thus be serviced one after
another, in the order of their priority, until the main
program eventually resumes.
INT 4
CPL = 7
MAIN
INTERRUPT 2 HAS PRIORITY LEVEL 2
INTERRUPT 3 HAS PRIORITY LEVEL 3
INTERRUPT 4 HAS PRIORITY LEVEL 4
INTERRUPT 5 HAS PRIORITY LEVEL 5
Figure
19) the