Intel UPI-C42 Computer Hardware User Manual


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UPI-C42UPI-L42
Table 1 Pin Description (Continued)
DIP PLCC QFP
Symbol Pin Pin Pin Type Name and Function
No No No
P
20
–P
27
21–24 24–27 39–42 IO PORT 2 8-bit PORT 2quasi-bidirectional IO lines The lower 4 bits
(P
20
–P
23
) interface directly to the 8243IO expander device and
35–38 39–42 11 13–15
contain address and data information duringPORT 4–7 accessP
21
can be programmed to provide hardwareA20 gate support The upper
4 bits (P
24
–P
27
) can be programmed to provideinterrupt Request and
DMA Handshake capability Software control canconfigure P
24
as
Output Buffer Full (OBF) interrupt P
25
as Input Buffer Full (IBF)
interrupt P
26
as DMA Request (DRQ) and P
27
as DMA ACKnowledge
(DACK
)
PROG 25 28 43 IO PROGRAM Multifunction pin used as theprogram pulse input during
PROM programming
During IO expander access the PROGpin acts as an addressdata
strobe to the 8243 This pinshould be tied high if unused
V
CC
40 44 17 POWER
a
5V main power supply pin
V
DD
26 29 1 POWER
a
5V during normal operation
a
1275V during programming
operation Low power standby supply pin
V
SS
20 22 38 GROUND Circuit ground potential
290414–4
Figure 4 Block Diagram
3
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