P82C42PD datasheet(3/25 Pages) INTEL

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UPI-C42UPI-L42

Table 1 Pin Description

(Continued)

DIP

PLCC

QFP

Symbol

Type

Name and Function

P20–P27

21–24

24–27

39–42

I O

PORT 2

8-bit PORT 2 quasi-bidirectional IO lines The lower 4 bits

(P20–P23) interface directly to the 8243 IO expander device and

35–38

39–42

11 13–15

contain address and data information during PORT 4 – 7 access P21

can be programmed to provide hardware A20 gate support The upper

4 bits (P24–P27) can be programmed to provide interrupt Request and

DMA Handshake capability Software control can configure P24 as

Output Buffer Full (OBF) interrupt P25 as Input Buffer Full (IBF)

interrupt P26 as DMA Request (DRQ) and P27 as DMA ACKnowledge

(DACK)

PROG

PROGRAM

Multifunction pin used as the program pulse input during

PROM programming

During IO expander access the PROG pin acts as an addressdata

strobe to the 8243 This pin should be tied high if unused

VCC

POWER a

5V main power supply pin

VDD

POWER a

5V during normal operation a1275V during programming

operation Low power standby supply pin

VSS

GROUND

Circuit ground potential

290414 – 4

Figure 4 Block Diagram

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