BVME4000/6000
54
Copyright
1993,1995,1998,2001 BVM Ltd.
7.13.4 Port C Usage
The MC68230 port C is nominally an 8 bit general purpose I/O port (similar to Ports A & B). However
five of the pins carry special functions associated with interrupts and timer operation.
The PORT SERVICE REQUEST REGISTER should be set up to use vectored interrupts on PIRQ and
PIACK. Thus bits 4 & 3 should be set as: Bit 4 SET, Bit 3 SET. The PORT INTERRUPT VECTOR
REGISTER should be set up with the required Interrupt vector.
The TIMER CONTROL REGISTER should be set up to use vectored interrupts on TOUT and TIACK.
Thus bits 7 & 6 should be set as: Bit 7 SET, Bit 6 CLEAR. Bit 5 should be used as an interrupt enable
bit. The TIMER INTERRUPT VECTOR REGISTER should be set up with the required Interrupt vector.
D7
D6
D5
D4
D3
D2
D1
D0
Special
Special
Special
IN/OUT
Special
Special
OUT
OUT
/TIACK
/PIACK
/PIRQ
WDOG
TOUT
TIN
PADIR
PAEN
Bit 7:
/TIACK: Timer Interrupt Acknowledge.
The Interrupt Controller assumes that the MC68230 Timer Interrupter supports vectored
interrupts. This pin is connected to the Interrupt Controller's TIMIACK line.
Bit 6:
/PIACK: Parallel Port Interrupt Acknowledge.
The Interrupt Controller assumes that the MC68230 Parallel Interrupter supports vectored
interrupts. This pin is connected to the Interrupt Controller's PARIACK line.
Bit 5:
/PIRQ: Parallel Port Interrupt Request.
This output drives the 68230 Parallel Interrupt input to the Interrupt Controller - refer to "7.8
Interrupt Controller (on page 35)" for more details.
Bit 4:
WDOG: WatchDog Refresh.
This bit drives the input to the watchdog circuit. When this bit is configured as an INPUT, the
watchdog function is disabled. When configured as an OUTPUT, the watchdog is enabled and
this bit must be toggled every second if a Watchdog time out is to be avoided. If the WDOG bit
is not toggled within the time out period (1 second minimum) then a hardware reset will be
generated.
Bit 3:
TOUT: Timer Output.
This output drives the 68230 Timer Interrupt input to the Interrupt Controller - refer "7.8
Interrupt Controller (on page 35)" for more details.
Bit 2:
TIN: Timer Input.
This input is driven from the T1 output of the DP8570A - refer to "7.12 Real Time
Clock/Timers (on page 50)" for more details.
Bit 1:
PADIR: Port A Direction.
This OUTPUT controls the DIRECTION of the transceiver. When SET the transceiver will
drive OUT from the BVME4000/6000 to the connector. When CLEAR the transceiver will
receive IN from the connector and drive into Port A.
Bit 0:
PAEN: Port A Enable.
This OUTPUT controls the ENABLE to the transceiver. When SET the transceiver is disabled
and its outputs are hi-impedance. When CLEAR the transceiver is enabled and will drive in the
direction controlled by its DIRECTION input.
Содержание BVME4000
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