mc68hc705j2 Freescale Semiconductor, Inc, mc68hc705j2 Datasheet - Page 49

• Manufacturer Part Number: mc68hc705j2
• Description: 8-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

5.2 Interrupts
MC68HC705J2
An interrupt temporarily stops normal processing to process a particular event.
Unlike a reset, an interrupt does not stop the operation of the instruction being
executed. An interrupt takes effect when the current instruction completes its
execution. An interrupt saves the CPU registers on the stack and loads the
program counter with a user-defined interrupt vector address. The following
conditions produce an interrupt:
The CPU does the following things to begin servicing an interrupt:
• Timer overflow or real-time interrupt request (timer interrupts)
• A logical zero applied to the IRQ pin (external interrupt)
• SWI instruction (software interrupt)
• Stores the contents of the CPU registers on the stack as shown in Figure
• Sets the interrupt mask to prevent further interrupts
• Loads the program counter with the contents of the appropriate interrupt
5-2
vector locations:
— $0FF8 and $0FF9 (timer interrupt vector)
— $0FFA and $0FFB (external interrupt vector)
— $0FFC and $0FFD (software interrupt vector)
Figure 5-2. Interrupt Stacking Order
STACK
RESETS AND INTERRUPTS
7
(HIGHEST STACK ADDRESS IS $00
(LOWEST STACK ADDRESS IS $0
TOWARD HIGHER ADDRESSES
TOWARD LOWER ADDRESSES
CONDITION CODE REGIST
PROGRAM COUNTER HIGH
PROGRAM COUNTER LOW
INDEX REGISTER
ACCUMULATOR
0
UNSTACK
MOTOROLA
5-3