Circuitos Integrados

8255A
Programmable peripheral interface
PDF datasheet
       
PA3 1  • 40 PA4
PA2 2 39 PA5
PA1 3 38 PA6
PA0 4 37 PA7
RD 5 36 WR
CS 6 35 RESET
GND 7 34 D0
A1 8 33 D1
A0 9 32 D2
PC7 10 31 D3
PC6 11 30 D4
PC5 12 29 D5
PC4 13 28 D6
PC0 14 27 D7
PC1 15 26 Vcc
PC2 16 25 PB7
PC3 17 24 PB6
PB0 18 23 PB5
PB1 19 22 PB4
PB2 20 21 PB3
       
Pin Symbol Description
1 PA3 port A
2 PA2 port A
3 PA1 port A
4 PA0 port A
5 RD read enable (active low)
6 CS chip select (active low)
7 GND ground
8 A1 address input
9 A0 address input
10 PC7 port C
11 PC6 port C
12 PC5 port C
13 PC4 port C
14 PC0 port C
15 PC1 port C
16 PC2 port C
17 PC3 port C
18 PB0 port B
19 PB1 port B
20 PB2 port B
21 PB3 port B
22 PB4 port B
23 PB5 port B
24 PB6 port B
25 PB7 port B
26 Vcc supply voltage
27 D7 data bus
28 D6 data bus
29 D5 data bus
30 D4 data bus
31 D3 data bus
32 D2 data bus
33 D1 data bus
34 D0 data bus
35 RESET reset (active high)
36 WR write enable (active low)
37 PA7 port A
38 PA6 port A
39 PA5 port A
40 PA4 port A

Notes
  • Register 00: read/write port A
  • Register 01: read/write port B
  • Register 10: read/write port C
  • Register 11: read/write control word
  • Control word:
    Bit 0 Port C lower bits; 1=input, 0=output
    Bit 1 Port B; 1=input, 0=output
    Bit 2 Group B mode selection
    Bit 3 Port C upper bits; 1=input, 0=output
    Bit 4 Port A; 1=input, 0=output
    Bits 5-6 Group A mode selection
    Bit 7 1=mode set, 0=bit set/reset

  • When bit 7 of control word is set to 1, the rest of the bits have the following functions:
    Bit 0 1=set bit, 0=clear bit
    Bits 1-3 specify bit to modify (0-7)

Note
Data is maintained by an independent source and accuracy is not guaranteed. Check with the manufacturer's datasheet for up-to-date information.

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