8741AH datasheet(5/20 Pages) INTEL

5 / 20 page

UPI-41AH42AH

P26 and P27 are port pins or DMA handshake pins

for use with a DMA controller These pins default

to port pins on Reset

If the ‘‘EN DMA’’ instruction has been executed

P26 becomes the DRQ (DMA Request) pin A ‘‘1’’

written to P26 causes a DMA request (DRQ is acti-

vated)

DRQ

deactivated

DACK

WR or execution of the ‘‘EN DMA’’ in-

struction

If ‘‘EN DMA’’ has been executed P27 becomes

the DACK (DMA ACKnowledge) pin This pin acts

as a chip select input for the Data Bus Buffer reg-

isters during DMA transfers

210393 – 7

DMA Handshake Capability

EN DMA

Op Code 0E5H

110010

When EA is enabled on the UPI the program

counter is placed on Port 1 and the lower three

bits of Port 2 (MSB e P22 LSB e P10) On the

UPI this information is multiplexed with PORT

DATA (see port timing diagrams at end of this

data sheet)

The 8741AH and 8742AH support the inteligent

Programming Algorithm (See the Programming

Section)

210393 – 8

Figure 5 8088-UPI-41AH42AH Interface

210393 – 10

Figure 6 8048H-UPI-4142 Interface

210393 – 9

Figure 7 UPI-4142-8243 Keyboard Scanner

APPLICATIONS

210393 – 30

Figure 4 UPI-41AH42AH Keyboard Controller

8741AH Datasheet(PDF) 5 Page - Intel Corporation