Standard Operation for Maskable Interrupts
3-16
If you want the ISR to inform a peripheral that the interrupt is being serv-
iced, you can use the IACK instruction to send an interrupt acknowledge
signal. The IACK instruction accepts a 16-bit constant as an operand. For
a detailed description of the IACK instruction, see Chapter 6, C28x As-
sembly Language Instructions.
14) Program continues. If the interrupt is not approved by the CPU, the inter-
rupt is ignored, and the program continues uninterrupted. If the interrupt
is approved, its interrupt service routine is executed and the program con-
tinues where it left off (at the return address).
Example 3−1. Typical ISR
C28x Full Context Save/Restore
INTX: .; 8 cycles
PUSH AR1H:AR0H ; 32-bit
PUSH XAR2 ; 32-bit
PUSH XAR3 ; 32-bit
PUSH XAR4 ; 32-bit
PUSH XAR5 ; 32-bit
PUSH XAR6 ; 32-bit
PUSH XAR7 ; 32-bit
PUSH XT ; 32-bit
; +8 = 16 cycles
.
.
.
POP XT
POP XAR7
POP XAR6
POP XAR5
POP XAR4
POP XAR3
POP XAR2
POP XAR1H;AR0H
IRET
; 16 cycles
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