Datasheet

Exception Control
MC68HC908GZ60 • MC68HC908GZ48 • MC68HC908GZ32 Data Sheet, Rev. 6
Freescale Semiconductor 231
Figure 15-11. Interrupt Recognition Example
15.5.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an interrupt regardless of the state of the
interrupt mask (I bit) in the condition code register.
NOTE
A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
15.5.1.3 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt sources. Table 15-3 summarizes the
interrupt sources, hardware flag bits, hardware interrupt mask bits, interrupt status register flags, interrupt
priority, and exception vectors. The interrupt status registers can be useful for debugging.
Interrupt Status Register 1
IF6–IF1 — Interrupt Flags 1–6
These flags indicate the presence of interrupt requests from the sources shown in Table 15-3.
1 = Interrupt request present
0 = No interrupt request present
Bit 0 and Bit 1 — Always read 0
Address: $FE04
Bit 7654321Bit 0
Read: IF6 IF5 IF4 IF3 IF2 IF1 0 0
Write:RRRRRRRR
Reset:00000000
R= Reserved
Figure 15-12. Interrupt Status Register 1 (INT1)
CLI
LDA
INT1
PULH
RTI
INT2
BACKGROUND
#$FF
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
PSHH
INT2 INTERRUPT SERVICE ROUTINE
ROUTINE