82C55A_06 Datasheet, PDF (15/29 Pages) Intersil Corporation – CMOS Programmable Peripheral Interface

82C55A
Modes 1 or 2, Port C generates or accepts “hand shaking”
signals with the peripheral device. Reading the contents of
Port C allows the programmer to test or verify the “status” of
each peripheral device and change the program flow
accordingly.
There is not a special instruction to read the status
information from Port C. A normal read operation of Port C is
executed to perform this function.
INTERRUPT
ENABLE FLAG
POSITION
ALTERNATE PORT C
PIN SIGNAL (MODE)
INTE B
PC2
ACKB (Output Mode 1)
or STBB (Input Mode 1)
INTE A2
PC4
STBA (Input Mode 1 or Mode
2)
INTE A1
PC6
ACKA (Output Mode 1 or
Mode 2)
FIGURE 17. INTERRUPT ENABLE FLAGS IN MODES 1 AND 2
Applications of the 82C55A
The 82C55A is a very powerful tool for interfacing peripheral
equipment to the microcomputer system. It represents the
optimum use of available pins and is flexible enough to
interface almost any I/O device without the need for
additional external logic.
Each peripheral device in a microcomputer system usually
has a “service routine” associated with it. The routine
manages the software interface between the device and the
CPU. The functional definition of the 82C55A is programmed
by the I/O service routine and becomes an extension of the
system software. By examining the I/O devices interface
characteristics for both data transfer and timing, and
matching this information to the examples and tables in the
detailed operational description, a control word can easily be
developed to initialize the 82C55A to exactly “fit” the
application. Figures 18 through 24 present a few examples
of typical applications of the 82C55A.
INTERRUPT
REQUEST
PC3 PA0
PA1
PA2
PA3
PA4
PA5
MODE 1
(OUTPUT)
PA6
PA7
PC7
PC6
PC5
PC4
82C55A
PB0
PB1
PB2
PB3
PB4
MODE 1 PB5
(OUTPUT) PB6
PB7
PC1
PC2
PC0
DATA READY
ACK
PAPER FEED
FORWARD/REV.
DATA READY
ACK
HIGH SPEED
PRINTER
HAMMER
RELAYS
PAPER FEED
FORWARD/REV.
RIBBON
CARRIAGE SEN.
INTERRUPT
REQUEST
CONTROL LOGIC
AND DRIVERS
FIGURE 18. PRINTER INTERFACE
15
FN2969.10
November 16, 2006