MOTOROLA
MC68HC11C0
40
MC68HC11C0TS/D
6.1 External Interrupt Requests
The MC68HC11C0 has a total of nine external interrupt inputs. In addition to the two external interrupts
found on other M68HC11 devices (IRQ and XIRQ), seven more inputs for interrupt requests have been
added. The seven additional inputs have been implemented as alternate functions of port F pins. The
interrupt request inputs IRQ[6:0] are individually enabled by bits in the FINTEN register. The IRQ and
XIRQ inputs have been moved and are now alternate functions of port D.
The IRQ and IRQ[6:0] interrupt sources are maskable and share the same priority. These interrupt
sources can be masked globally by bit I in the condition code register as well as locally by enable bits
in control registers. IRQ[6:0] are enabled by bits in the FINTEN register. IRQ is enabled by bits in DIO-
CTL register. Since IRQ[6:0] have the same priority as IRQ, software must poll an interrupt status reg-
ister (FISTAT) to determine the source of the interrupt request. FISTAT is automatically cleared when
it is read by the CPU. FISTAT can be read at any time but cannot be written. Refer to the descriptions
of port F, FINTEN and FISTAT.
When corresponding bits in FINTEN are set, port F lines become interrupt request inputs. Writes to
PORTF drive pins only if the pins are configured for output and corresponding IRQ is disabled.
IS7 is the interrupt status bit for IRQ in port D. FISTAT can be read any time but cannot be written. All
bits are cleared after CPU has read the register following an interrupt request.
IS7 — IRQ Status
0 = No interrupt pending for the corresponding interrupt line
1 = Interrupt pending for the corresponding interrupt line
IS[6:0] — IRQ[6:0] Status
0 = No interrupt pending for the corresponding interrupt line
1 = Interrupt pending for the corresponding interrupt line
The enable bit for IRQ is located in the DIOCTL register.
IE[6:0] — IRQ[6:0] Enable
0 = Interrupt request input is disabled and pin is controlled by DDRF bit
1 = Interrupt request input IRQx is enabled, overriding state of DDRF bit
PORTF — Port F Data Register
$0002
Bit 7
654321
Bit 0
—
PF6
PF5
PF4
PF3
PF2
PF1
PF0
RESET:
0000000
0
Alt. Pin
Func.:
—
IRQ6
IRQ5
IRQ4
IRQ3
IRQ2
IRQ1
IRQ0
FISTAT — Port F Interrupt Status
$0004
Bit 7
654321
Bit 0
IS7
IS6
IS5
IS4
IS3
IS2
IS1
IS0
RESET:
00000000
FINTEN — Port F Interrupt Enable
$0005
Bit 7
654321
Bit 0
—
IE6
IE5
IE4
IE3
IE2
IE1
IE0
RESET:
00000000