ST92195D View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

ST92195D

48-96 Kbyte ROM HCMOS MCU WITH ON-SCREEN DISPLAY AND TELETEXT DATA SLICER

STMicroelectronics 

ST92195C/D - INTERRUPTS

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.

Example 1

In the first example, (simplest case, Figure 21 on

page 47) the ei instruction is not used within the

interrupt service routines. This means that no new

interrupt can be serviced in the middle of the cur-

rent one. The interrupt routines will thus be serv-

iced one after another, in the order of their priority,

until the main program eventually resumes.

Figure 21. Simple Example of a Sequence of Interrupt Requests with:

- Concurrent mode selected and

- IEN unchanged by the interrupt routines

0

Priority Level of

Interrupt Request

1

INTERRUPT 2 HAS PRIORITY LEVEL 2

INTERRUPT 3 HAS PRIORITY LEVEL 3

INTERRUPT 4 HAS PRIORITY LEVEL 4

INTERRUPT 5 HAS PRIORITY LEVEL 5

2

3

INT 2

4

INT 3

INT 4

5

INT 5

ei CPL = 7

6

INT 5

7

MAIN

CPL is set to 7

INT 2

CPL = 7

INT 3

CPL = 7

INT 4

CPL = 7

MAIN

CPL = 7

47/249

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