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JANUS? 2020 Hand-Held Computer (4MB) - Intermec

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Glossary<br />

G<br />

PC Standard communications protocol<br />

A communications protocol that handles data transfer on a character-bycharacter<br />

basis or by either filling a receive buffer or transmitting a buffer of<br />

data. This protocol is designed to be compatible with the standard PC BIOS<br />

functions. The one exception is that the PC Standard protocol can buffer data<br />

that is received to avoid losing characters if a program has not checked for data<br />

recently.<br />

physical RAM drive<br />

See RAM drive.<br />

Plessey Code<br />

A fixed length, continuous, and not self-checking bar code symbology. Plessey<br />

code is pulse-width modulated. It includes a start character, data characters, an<br />

eight-bit cyclic check digit, a termination bar, and usually a reverse start<br />

character.<br />

Point-to-Point protocol<br />

Point-to-Point is an unsolicited protocol in which the reader transmits data<br />

whenever it has something to transmit. The data is followed by a CR LF as the<br />

EOM characters. The reader is always in a receiving state and does not wait for<br />

select commands. This protocol does not perform any error checking or<br />

acknowledgment handshaking. Point-to-Point protocol is typically used to<br />

connect the reader to a CRT terminal or host computer.<br />

POL<br />

Poll character. Sent by the host to request reader data. For User-Defined<br />

Multi-Drop protocol, you must define a unique character for each reader on a<br />

data line.<br />

Polling Mode D<br />

Polling Mode D is a communications protocol that requires the host computer<br />

to ask the reader for data it might have (polling) and to request to send data to<br />

the reader (selecting). Polling Mode D is used to connect multiple devices to a<br />

single multiport controller. PC-IRL uses this protocol.<br />

POST<br />

Power-on self test. This test runs when you warm or cold boot the reader. The<br />

test ensures that the reader’s hardware and peripherals are operational.<br />

postamble<br />

A field of data that is sent after the data in a message. It is typically used to tag<br />

transactions from the bar code reader for rapid processing by the host, and it<br />

expands the data field (record) length. Similar to the preamble.<br />

G-19

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