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82C55A Datasheet, PDF (13/26 Pages) Intel Corporation – CHMOS PROGRAMMABLE PERIPHERAL INTERFACE | |||
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82C55A
MODE 0
MODE DEFINITION SUMMARY
MODE 1
MODE 2
IN
OUT
IN
OUT
GROUP A ONLY
PA0
In
Out
In
Out
PA1
In
Out
In
Out
PA2
In
Out
In
Out
PA3
In
Out
In
Out
PA4
In
Out
In
Out
PA5
In
Out
In
Out
PA6
In
Out
In
Out
PA7
In
Out
In
Out
PB0
In
Out
In
Out
PB1
In
Out
In
Out
PB2
In
Out
In
Out
PB3
In
Out
In
Out
PB4
In
Out
In
Out
PB5
In
Out
In
Out
PB6
In
Out
In
Out
PB7
In
Out
In
Out
Mode 0
or Mode 1
Only
PC0
In
Out
INTRB
INTRB
I/O
PC1
In
Out
IBFB
OBFB
I/O
PC2
In
Out
STBB
ACKB
I/O
PC3
In
Out
INTRA
INTRA
INTRA
PC4
In
Out
STBA
I/O
STBA
PC5
In
Out
IBFA
I/O
IBFA
PC6
In
Out
I/O
ACKA
ACKA
PC7
In
Out
I/O
OBFA
OBFA
Special Mode Combination Considerations
There are several combinations of modes possible. For any
combination, some or all of Port C lines are used for control
or status. The remaining bits are either inputs or outputs as
deï¬ned by a âSet Modeâ command.
During a read of Port C, the state of all the Port C lines,
except the ACK and STB lines, will be placed on the data
bus. In place of the ACK and STB line states, ï¬ag status will
appear on the data bus in the PC2, PC4, and PC6 bit
positions as illustrated by Figure 17.
Through a âWrite Port Câ command, only the Port C pins
programmed as outputs in a Mode 0 group can be written.
No other pins can be affected by a âWrite Port Câ command,
nor can the interrupt enable ï¬ags be accessed. To write to
any Port C output programmed as an output in Mode 1 group
or to change an interrupt enable ï¬ag, the âSet/Reset Port C
Bitâ command must be used.
With a âSet/Reset Port Cea Bitâ command, any Port C line
programmed as an output (including IBF and OBF) can be
written, or an interrupt enable ï¬ag can be either set or reset.
Port C lines programmed as inputs, including ACK and STB
lines, associated with Port C fare not affected by a
âSet/Reset Port C Bitâ command. Writing to the correspond-
ing Port C bit positions of the ACK and STB lines with the
âSet Reset Port C Bitâ command will affect the Group A and
Group B interrupt enable ï¬ags, as illustrated in Figure 17.
INPUT CONFIGURATION
D7 D6 D5 D4 D3 D2 D1 D0
I/O I/O IBFA INTEA INTRA INTEB IBFB INTRB
GROUP A
GROUP B
D7 D6
OBFA INTEA
OUTPUT CONFIGURATION
D5 D4 D3 D2 D1 D0
I/O I/O INTRA INTEB OBFB INTRB
GROUP A
GROUP B
FIGURE 15. MODE 1 STATUS WORD FORMAT
D7 D6 D5 D4 D3 D2 D1 D0
OBFA INTE1 IBFA INTE2 INTRA X
X
X
GROUP A
GROUP B
(Deï¬ned by Mode 0 or Mode 1 Selection)
FIGURE 16. MODE 2 STATUS WORD FORMAT
Current Drive Capability
Any output on Port A, B or C can sink or source 2.5mA. This
feature allows the 82C55A to directly drive Darlington type
drivers and high-voltage displays that require such sink or
source current.
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