Interrupt and Exception Handling
5-4
MC68322 USER’S MANUAL
MOTOROLA
The MC68322 completely decodes the address map and generates an internal DTACK. If
the core presents an address that does not match any of the programmed addresses for the
modules, none of the modules will generate DTACK. This condition is called an illegal
address. When an illegal address is detected, the core interface asserts an internal DTACK
and sets a level 7 interrupt to indicate an error condition. The software interrupt event
register’s CIA bit is then set, thus indicating that the core has accessed a memory location
that is not mapped to a register, chip-select, or DRAM. The interrupt is cleared by writing a
1 to the CIA bit position. The core will never have a bus error condition. The EIA bit is set if
the external bus master accesses a memory location that is not mapped to a register, chip-
select, or DRAM. This interrupt generates a level 7 interrupt to the core. The interrupt is
cleared by writing a 1 to the EIA bit position.
5.2 EXTERNAL INTERRUPTS
The MC68322 provides up to four pins for external interrupts (IRQ3–IRQ0). IRQ1 and IRQ0
are dedicated interrupt pins. IRQ3 and IRQ2 are multiplexed pins and must be programmed
to be used as interrupt pins. Refer to Appendix D Alternate Pin Functions for more details.
These inputs can be individually programmed for active polarity and either level or edge
sensitivity. External interrupts are asynchronous to the MC68322 and are synchronized
inside the MC68322 for proper operation. Two registers control each source of external
interrupt—external interrupt 0/2 and 1/3 registers (EXIR0/2–EXIR1/3). Figure 5-2 illustrates
these registers.
Figure 5-2. External Interrupt Registers (EXIR0/2–EXIR1/3)
= RESERVED
EXTERNAL
INTERRUPT
REGISTER 0/2
15
14
13
12
11
10
9
8
7
65432
1
0
15
14
13
12
11
10
9
8
7
65432
1
0
ENB0
00FFF770
00FFF772
00FFF774
00FFF776
00FFF778
00FFF780
00FFF782
00FFF784
00FFF786
00FFF788
REQ0
STS0
INTERRUPT
LEVEL
MODE0
SEN0
EXTERNAL
INTERRUPT
REGISTER 1/3
ENB1
REQ1
STS1
INTERRUPT
LEVEL
MODE1
SEN1
ENB2
STS2
STS3 REQ3
REQ2
MODE2
MODE3
SEN2
ENB3
SEN3
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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