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Chapter 5 Detailed Applications

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5.2.2

Writing Kernel(OS-dependent) Interrupt Handler

When describing the kernel(OS-dependent) interrupt handler in assembly language, observe the following pre-
cautions

1. At the beginning of file, be sure to include "mr308.inc" which is in the system directory.

2. For the symbol indicating the interrupt handler start address, make the external declara-

tion(Global declaration).

3. Make sure that the registers used in a handler are saved at the entry and are restored after

use.

4. Return to the task by ret_int service call.

.INCLUDE mr308.inc

------(1)

.GLB

inth

------(2)

inth:

; Registers used are saved to a stack

------(3)

iwup_tsk #ID_task1

:
process
:

; Registers used are restored

------(3)

ret_int

------(4)

Figure 5.8 Example of kernel(OS-depend) interrupt handler

Use the .GLB peudo-directive.