PD6710/’22 — ISA-to-PC-Card (PCMCIA) Controllers
15.3
ISA Bus DMA Handshake Signal
A DMA request from the card is passed to the ISA bus as long as the socket interface FIFO is
empty. IRQ10 is used as the DMA request output to the ISA bus when bit 2 of the Misc Control 2
register is ‘1’. When bit 2 of the Misc Control 2 register is ‘1’, IRQ9 is redefined as the active-low
DMA acknowledge input from the ISA bus. This signal must remain active for all DMA transfers
through the PD6722.
Figure 16. DMA Handshake Connections to the ISA Bus
to Make the PD6722 DMA-Capable
PD6722
DREQ
IRQ10
ISA
-DACK
IRQ9
Bus
TC
-VPP_VALID
Terminal counts are passed through to the card from the PD6722 -VPP_VALID pin when bit 6 of
the Misc Control 2 register is ‘1’. For a DMA write process, the last-cycle terminal count
condition is indicated by -OE being active-low during a card DMA data read cycle. For a DMA
read process, terminal count is indicated by -WE being active-low during the last card cycle.
15.4
Configuring the PD6722 Registers for a DMA Transfer
Program the registers as follows to configure a PD6722 socket interface for DMA transfer to/from
a DMA-capable PC Card:
1. Select which pin on the PC Card interface will serve as the DMA request input.
2. Configure the socket interface as I/O-capable.
3. Prevent dual-interpretation of socket interface DMA handshake signals.
4. Set the DMA Enable bit.
15.4.1
Programming the DMA Request Pin from the Card
The PD6722 allows selection of one from three PC Card interface inputs to be redefined as the
DMA request input, and it also allows programming of the active level of the selected input. This is
done by setting bits 7 and 6 of the Extension Control 1 register to the desired values matching
those of the DMA-capable PC Card to be used.
Once this selection of DMA request input is complete, the PC Card interface is configured at the
signal level for DMA card interfacing.
The following table shows how the PD6722 socket interface signals are redefined when a card is in
DMA card interface mode:
98
Datasheet
INTEL [ INTEL ]
