mc68hc908kx8 Freescale Semiconductor, Inc, mc68hc908kx8 Datasheet - Page 143

• Manufacturer Part Number: mc68hc908kx8
• Description: M68hc08 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

13.5 Program Exception Control
Normal, sequential program execution can be changed in two ways:
13.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the
interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the return-from-interrupt
(RTI) instruction recovers the CPU register contents from the stack so that normal processing can
resume.
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The
arbitration result is a constant that the CPU uses to determine which vector to fetch. As shown in
13-9, once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of
priority, until the latched interrupt is serviced or the I bit is cleared.
Freescale Semiconductor
INTERRUPT
1. Interrupts
2. Reset
INTERRUPT
MODULE
I BIT
I BIT
R/W
R/W
IDB
IDB
IAB
IAB
MODULE
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
Figure 13-7
DUMMY
MC68HC908KX8 • MC68HC908KX2 • MC68HC08KX8 Data Sheet, Rev. 2.1
DUMMY
shows interrupt entry timing.
SP – 4
SP
PC – 1[7:0] PC – 1[15:8]
CCR
SP – 1
SP – 3
Figure 13-8. Interrupt Recovery
Figure 13-7
A
SP – 2
SP – 2
X
X
.
Figure 13-8
SP – 3
SP – 1
Interrupt Entry
PC – 1 [7:0] PC – 1 [15:8] OPCODE
A
SP – 4
SP
shows interrupt recovery timing.
CCR
VECT H
PC
V DATA H
VECT L START ADDR
PC + 1
OPERAND
V DATA L
Program Exception Control
OPCODE
Figure
143