
INTERRUPT STRUCTURE
S3C8248/C8245/P8245/C8247/C8249/P8249
5-14
INTERRUPT PENDING FUNCTION TYPES
Overview
There are two types of interrupt pending bits: one type that is automatically cleared by hardware after the
interrupt service routine is acknowledged and executed; the other that must be cleared in the interrupt service
routine.
Pending Bits Cleared Automatically by Hardware
For interrupt pending bits that are cleared automatically by hardware, interrupt logic sets the corresponding
pending bit to "1" when a request occurs. It then issues an IRQ pulse to inform the CPU that an interrupt is
waiting to be serviced. The CPU acknowledges the interrupt source by sending an IACK, executes the service
routine, and clears the pending bit to "0". This type of pending bit is not mapped and cannot, therefore, be read or
written by application software.
In the S3C8248/C8245/C8247/C8249 interrupt structure, the timer 0 overflow interrupt (IRQ0) belongs to this
category of interrupts in which pending condition is cleared automatically by hardware.
Pending Bits Cleared by the Service Routine
The second type of pending bit is the one that should be cleared by program software. The service routine must
clear the appropriate pending bit before a return-from-interrupt subroutine (IRET) occurs. To do this, a "0" must
be written to the corresponding pending bit location in the source’s mode or control register.
Summary of Contents for C8245
Page 31: ...ADDRESS SPACES S3C8248 C8245 P8245 C8247 C8249 P8249 2 20 NOTES ...
Page 107: ...INTERRUPT STRUCTURE S3C8248 C8245 P8245 C8247 C8249 P8249 5 18 NOTES ...
Page 195: ...INSTRUCTION SET S3C8248 C8245 P8245 C8247 C8249 P8249 6 88 NOTES ...
Page 221: ...I O PORTS S3C8248 C8245 P8245 C8247 C8249 P8249 9 16 NOTES ...
Page 245: ...16 BIT TIMER 0 1 S3C8248 C8245 P8245 C8247 C8249 P8249 12 10 NOTES ...
Page 249: ...WATCH TIMER S3C8248 C8245 P8245 C8247 C8249 P8249 13 4 NOTES ...
Page 267: ...A D CONVERTER S3C8248 C8245 P8245 C8247 C8249 P8249 15 6 NOTES ...
Page 299: ...S3P8245 P8249 OTP S3C8248 C8245 P8245 C8247 C8249 P8249 21 8 NOTES ...
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