Справочник Пользователя для National Instruments PC-DIO-24

1, 3, 5, 7, 9, 11, 13,
15

PC<7..0>

Port C—Bidirectional data lines for port C.  PC7 is the MSB,
PC0 the LSB.

17, 19, 21, 23, 25,
27, 29, 31

PB<7..0>

Port B—Bidirectional data lines for port B.  PB7 is the MSB,
PB0 the LSB.

33, 35, 37, 39, 41,
43, 45, 47

PA<7..0>

Port A—Bidirectional data lines for port B.  PA7 is the MSB,
PA0 the LSB.

49 (see note below)

+5 V

+5 Volts—This pin provides +5 VDC.

All even-numbered
pins

GND

Ground—These signals are connected to the PC ground signal.

The absolute maximum voltage input rating is -0.5 to +5.5 V with respect to GND.

The signals assigned to port C depend on the mode in which the 82C55A is programmed.  In
mode 0, port C is considered two 4-bit I/O ports.  In modes 1 and 2, port C is used for status and
handshaking signals with two or three I/O bits mixed in.  Table 2-2 summarizes the signal
assignments of port C for each programmable mode.  See Chapter 4, Register-Level
Programming, for register-level programming information.

Table 2-2.  Port C Signal Assignments

Programming Mode

Mode 0

I/O

I/O

I/O

I/O

I/O

I/O

I/O

I/O

Mode 1 Input

I/O

I/O

IBFA

STBA*

INTRA

STBB*

IBFBB

INTRB

Mode 1 Output

OBFA*

ACKA* I/O

I/O

INTRA

ACKB* OBFB*

INTRB

Mode 2

OBFA*

ACKA* IBFA

STBA*

INTRA

I/O

I/O

I/O

* Indicates that the signal is active low.