AN2109 Freescale Semiconductor / Motorola, AN2109 Datasheet - Page 42

• Manufacturer Part Number: AN2109
• Description: MPC555 Interrupts
• Manufacturer: Freescale Semiconductor / Motorola

Freescale Semiconductor, Inc.
7.3.5 Example 5: ISR Using C Only – General Case
Summary: This is a more general case interrupt exception implemented entirely in C for the same SCI
function as in prior examples.
Operation: Ext_Isr function now tests for each of the 16 possible interrupt sources. As in prior exam-
ples, there is only one interrupt source implemented.
Remember, unless using exception table relocation (ETRE = 1), the Ext_Isr must be less than 256 bytes
long because another exception vector starts again.
Stack Frame: This particular example saves additional registers, namely the rest of the gprs except
gpr2 and gpr13. (These are small data anchors defined in the EABI). Hence this stack frame size is 152
bytes.
MPC555 Interrupts
MOTOROLA
Rev. 0, 26 July 2001
42
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