82C55A Intersil Corporation, 82C55A Datasheet - Page 8

• Manufacturer Part Number: 82C55A
• Description: CMOS Programmable Peripheral Interface
• Manufacturer: Intersil Corporation

Mode 0 Configurations
Operating Modes
Mode 1 - (Strobed Input/Output). This functional configura-
tion provides a means for transferring I/O data to or from a
specified port in conjunction with strobes or “hand shaking”
signals. In mode 1, port A and port B use the lines on port C
to generate or accept these “hand shaking” signals.
Mode 1 Basic Function Definitions:
• Two Groups (Group A and Group B)
• Each group contains one 8-bit port and one 4-bit
• The 8-bit data port can be either input or output. Both
• The 4-bit port is used for control and status of the 8-bit
Input Control Signal Definition
(Figures 6 and 7)
STB (Strobe Input)
A “low” on this input loads data into the input latch.
IBF (Input Buffer Full F/F)
A “high” on this output indicates that the data has been
loaded into the input latch: in essence, and acknowledg-
ment. IBF is set by STB input being low and is reset by the
rising edge of the RD input.
CONTROL WORD #12
CONTROL WORD #13
control/data port
inputs and outputs are latched.
port.
D7 - D0
D7 - D0
D7
D7
1
1
D6
D6
0
0
D5
D5
0
0
D4
D4
1
1
D3
D3
1
1
D2
D2
0
0
82C55A
82C55A
D1
D1
0
0
(Continued)
C
C
D0
D0
0
1
A
B
A
B
8
4
4
8
8
4
4
8
PC7 - PC4
PC3 - PC0
PB7 - PB0
PC7 - PC4
PC3 - PC0
PB7 - PB0
PA7 - PA0
PA7 - PA0
82C55A
8
CONTROL WORD #14
CONTROL WORD #15
CONTROL WORD
CONTROL WORD
D7
D7 D6 D5 D4 D3 D2 D1 D0
1
1
D7 - D0
D7 - D0
D7
D7
1
1
D6
0
D6
D6
0
0
D5
1
D5
D5
0
0
D4
1
D4
D4
1
1
1/0
D3 D2 D1 D0
FIGURE 6. MODE 1 INPUT
D3
D3
1
1
1
PC6, PC7
1 = INPUT
0 = OUTPUT
D2
D2
0
0
82C55A
82C55A
1
RD
RD
D1
D1
1
1
C
C
D0
D0
0
1
A
B
A
B
MODE 1 (PORT A)
MODE 1 (PORT B)
INTE
INTE
A
B
8
4
4
8
8
4
4
8
PC6, PC7
PB7-PB0
PA7-PA0
PC7 - PC4
PC3 - PC0
PB7 - PB0
PC7 - PC4
PC3 - PC0
PB7 - PB0
PA7 - PA0
PA7 - PA0
PC4
PC5
PC3
PC2
PC1
PC0
2
8
8
STBA
IBFA
INTRA
STBB
IBFB
INTRB
I/O