82C55A Datasheet, PDF (12/23 Pages) Intel Corporation – CHMOS PROGRAMMABLE PERIPHERAL INTERFACE

82C55A
Output Control Signal Definition
OBF (Output Buffer Full F F) The OBF output will
go ‘‘low’’ to indicate that the CPU has written data
out to the specified port The OBF F F will be set by
the rising edge of the WR input and reset by ACK
Input being low
ACK (Acknowledge Input) A ‘‘low’’ on this input
informs the 82C55A that the data from Port A or Port
B has been accepted In essence a response from
the peripheral device indicating that it has received
the data output by the CPU
INTR (Interrupt Request) A ‘‘high’’ on this output
can be used to interrupt the CPU when an output
device has accepted data transmitted by the CPU
INTR is set when ACK is a ‘‘one’’ OBF is a ‘‘one’’
and INTE is a ‘‘one’’ It is reset by the falling edge of
WR
INTE A
Controlled by bit set reset of PC₆
INTE B
Controlled by bit set reset of PC₂
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Figure 10 MODE 1 Output
Figure 11 MODE 1 (Strobed Output)
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