Theory of Operation
Chapter 3
AT-DIO-32F User Manual
3-10
© National Instruments Corporation
Figure 3-8 shows a write transfer in trailing edge mode.
After TDELAY
Wait
DRDY
INIT
State
REQ unasserted
REQ
asserted
When WRITE bit
and DIOxEN bit
for group are set
Send ACK
Start TDELAY
LRESET
or
Power On
Clear
ACK
Figure 3-8. Trailing Edge Mode – Write
Interrupt Control Circuitry
The interrupt control circuitry routes any enabled interrupts to the selected interrupt request lines.
Eleven interrupt request lines are available for use by the AT-DIO-32F: IRQ3, IRQ4, IRQ5,
IRQ6, IRQ7, IRQ9, IRQ10, IRQ11, IRQ12, IRQ14, and IRQ15. Group 1 and Group 2 can each
be set to have an interrupt request line. With the interrupt requests, which are tri-state output
signals, the AT-DIO-32F board can share the interrupt lines with other devices. Five different
interrupts can be generated by the AT-DIO-32F: DRDY1 set, DRDY2 set, Group 1 DMA
terminal count received, Group 2 DMA terminal count received, and a rising edge on Counter 3
received. Each one of these interrupts is individually enabled and cleared. See Chapter 4,
Programming, for additional information about programming with interrupts.
DMA Control Circuitry
Each handshaking group can be assigned a separate DMA channel for 16-bit data transfer, and
each group has a DMA enable bit, DMAEN. When DMA is enabled, the AT-DIO-32F sends a
DMA request to a port that is ready to receive data during a write transfer, or to a port that is
ready to read data during a read transfer. DMA channels 5, 6, and 7 of the PC I/O channel are
available for such transfers.
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