Chapter 8
Communication Protocols
This chapter describes the communication protocols used by
SmartPass
®
.
Overview
SmartPass readers support the following communication protocols:
•
Basic protocol
•
Error correcting protocol
•
Data inquiry protocol
The following protocol information provides reference information relevant to
developing host interface software.
A two-way message interchange is required in both data mode and command mode
with error correcting protocol. This interchange is completed by the message
recipient issuing a message.
With error correcting protocol (ECP), all transmissions require a message. If a
message is not received, the sender will timeout with the same effect as if it had
received a negative acknowledgment (from host) or an
Error
message (from
reader).
XON/XOFF
flow control is optionally supported. Be careful in the use of
XON/XOFF
because noise-induced characters may be interpreted by the reader as the
XOFF
character, which would suspend reader output without the host computer’s
knowledge.
Note:
TransCore recommends that XON/XOFF flow control be disabled while
using the ECP.
Communications are performed using the 7-bit ASCII code with optional parity, thus
providing easy setup, testing, and diagnostics with standard ASCII terminals and
serial printers. Parity must be enabled to achieve the specified undetected error rate.
Each message is framed with the start-of-message (som) and end-of-message (eom)
characters so that the host computer can detect the beginning and end of each
message. This convention is most important under marginal communications
conditions during which the host may receive extraneous noise-induced characters
between reader transmissions. In such instances, the host is able to ignore any
messages that do not conform to the som...eom frame sequence.
8-3
Содержание SmartPass AI1611
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Страница 17: ...A Glossary...
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Страница 23: ...B System Specifications...
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Страница 27: ...C Wiring Tables...
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Страница 33: ...1 Introduction...
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Страница 41: ...2 Preparing the Site...
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Страница 53: ...3 Quick SmartPass Test...
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