Intermec Transaction Manager 9560, Руководство пользователя

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9560 Transaction Manager User’s Manual
5-6
The XON or the XOFF character may match the LRC (Longitudinal
Redundancy Check character). If so, the LRC is never checked for
transparency. It is always treated as a parameter.
Received data is also checked for a DLE. The XON or XOFF character is
interpreted as data if XON/XOFF flow control is enabled and the character is
preceded by a DLE. In User-Defined protocol, the reader allows flow control to
be implemented along with an LRC. The reader knows when the LRC character
is expected. It does not perform the XON or XOFF character check when the
LRC is the next character expected.
Working With Protocols
Data link protocols govern the way data is transmitted. They provide the
framework for an orderly exchange of data between computers, terminals, and
data collection devices. With most protocols, the reader (slave) never
communicates unless the host (master) initiates the transaction with a
poll/select sequence. Point-to-Point protocol is the exception.
Polling Mode D and Multi-Drop are very secure data link protocols designed
to interface with the Intermec 9154 Network Controller and 9161 Port
Concentrator. Both devices continuously poll bar code readers and printers for
transactions and pass those transactions to the host computer.
Both Polling Mode D and Multi-Drop provide recovery from transmission
errors (parity and framing errors) and use affirmative and negative responses
to verify successful and unsuccessful communication events. If the transmitting
device receives a negative acknowledgment, the data is retransmitted.
You use User-Defined and User-Defined Multi-Drop protocols to develop a
custom protocol. You can define how secure the data link protocol will be and
implement a master/slave data link with error recovery.
Point-to-Point Protocol
Point-to-Point protocol is designed specifically for Intermec readers where the
reader is connected to a terminal or a host computer. Point-to-Point protocol
has the following characteristics:
Full-duplex This protocol can send and receive data simultaneously.
Asynchronous
The data is sent one character at a time.
Nonpolling
The solicitation (POL) and handshake sequences (XON/XOFF) are
disabled.
Whenever data is available to transmit, the data is transmitted immediately.
You can control the flow of data by enabling XON/XOFF or by sending the
CTS command (Clear to Send) from the host.