CL-PD6722 datasheet(85/128 Pages) CIRRUS

85 / 128 page

CL-PD6710/’22

ISA–to–PC-Card Host Adapters

May 1997

PRELIMINARY DATA SHEET v3.1

DMA OPERATION (CL-PD6722 only)

14.4.1

Programming the DMA Request Pin from the Card

The CL-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 set-

ting 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 CL-PD6722 socket interface signals are redeﬁned when a card is in

DMA card interface mode:

Figure 14-2. Card DMA Request and Acknowledge Handshake with Terminal Count

Notice that the DMA acknowledge to the card as -REG high is only active during the actual DMA read or

write card cycle. This means there is no mechanism to deassert DACK to the card: The card must under-

stand that receiving the ﬁrst DMA cycle

is its DMA acknowledgment.

Standard I/O Card

Interface Signal Name

DMA-Capable Card Interface

Signal Usage

When Signal Redeﬁnition for DMA

Interface is Effective

-IOIS16

-IOIS16 or may be selected as the active-low

DMA request input

Extension Control 1 register bits 7-6 = ‘10’

(BVD2/)

-SPKR/-LED

-SPKR/-LED or may be selected as the

active-low DMA request input

Extension Control 1 register bits 7-6 = ‘11’

-INPACK

-INPACK or may be selected as the active-

low DMA request input

Extension Control 1 register bits 7-6 = ‘01’

-REG

-REG during standard cycles, active-high

DACK during DMA read/write cycles

Only during actual card DMA read or write

cycle

-OE

-OE during standard cycles, active-low -TC

during DMA write cycles

During DMA write cycles (that is, when

-REG is high and -IORD is low)

-WE

-WE during standard cycles, active-low -TC

during DMA read cycles

During DMA read cycles (that is, when -REG

is high and -IOWR is low)

-DREQ

DACKa

PC Card

CL-PD6722

-REG

-IOIS16, -SPKR, or -INPACK

-REG

a A DMA cycle is the DMA acknowledge to the card.

-TC

-OE/-WE

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