8255 – programmable parallel port device
Post on 31-Dec-2015
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8255 – PROGRAMMABLE PARALLEL PORT DEVICE. METHODS OF PARALLEL DATA TRANSFER. SIMPLE INPUT AND OUTPUT SIMPLE STROBE I/O SINGLE-HANDSHAKE I/O DOUBLE HANDSHAKE I/O. HANDSHAKE INPUT DATA TRANSFER SIGNAL DIRECTIONS. MICRO- PROCESSOR. PORT DEVICE. PERIPHERAL. PARALLEL DATA LINES. - PowerPoint PPT Presentation
TRANSCRIPT
8255 – PROGRAMMABLE PARALLEL PORT DEVICE
METHODS OF PARALLEL DATA TRANSFER
• SIMPLE INPUT AND OUTPUT• SIMPLE STROBE I/O• SINGLE-HANDSHAKE I/O• DOUBLE HANDSHAKE I/O
HANDSHAKE INPUT DATA TRANSFER SIGNAL DIRECTIONS
MICRO-
PROCESSORPERIPHERAL
PARALLELDATA LINES
PORTDEVICE
STB
ACK
Need of 8255
• The parallel port device 8255 has been designed to automatically manage the handshake operation.
• Eg, it can be programmed to automatically receive an Strobe signal from a peripheral, send an int signal to the processor and send the ACK signal back to the peripheral at proper times
8255 – Internal block diagram
Note: 8255 is often used in mode 1
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