System Integration Block (SIB)
3-26
MC68302 USER’S MANUAL
MOTOROLA
NOTE
While in disable CPU mode, during the host processor interrupt
acknowledge cycle for IRQ1, if IRQ1 is not continuously assert-
ed, the interrupt controller will still provide the vector number
(and DTACK) according to the IV1 bit. The IACK6 falling edge
can be used externally to negate IRQ1.
1 = Edge-triggered. An interrupt is made pending when IRQ1 changes from one to
zero (falling edge).
V7–V5—Interrupt Vector Bits 7–5
These three bits are concatenated with five bits provided by the interrupt controller, which
indicate the specific interrupt source, to form an 8-bit interrupt vector number. If these bits
are not written, the vector $0F is provided.
Note:
These three bits should be greater than or equal to ‘010’ in order
to put the interrupt vector in the area of the exception vector ta-
ble for user vectors.
Bits 11 and 4–0—Reserved for future use.
3.2.5.2 Interrupt Pending Register (IPR)
Each bit in the 16-bit IPR corresponds to an INRQ interrupt source. When an INRQ interrupt
is received, the interrupt controller sets the corresponding bit in the IPR.
In a vectored interrupt environment, the interrupt controller clears the IPR bit when the vec-
tor number corresponding to the INRQ interrupt source is passed to the M68000 core during
an interrupt acknowledge cycle, unless an event register exists for that INRQ interrupt. In a
polled interrupt scheme, the user must periodically read the IPR. When a pending interrupt
is handled, the user should clear the corresponding bit in the IPR by writing a one to that bit.
(If an event register exists, the unmasked event register bits should be cleared instead,
causing the IPR bit to be cleared.) Since the user can only clear bits in this register, the bits
that are written as zeros will not be affected. The IPR is cleared at reset.
NOTE
The ERR bit is set if the user drives the IPL2–IPL0 lines to inter-
rupt level 4 and no INRQ interrupt is pending.
15
14
13
12
11
10
9
8
PB11
PB10
SCC1
SDMA
IDMA
SCC2
TIMER1
SCC3
7
6
5
4
3
2
1
0
PB9
TIMER2
SCP
TIMER3
SMC1
SMC2
PB8
ERR