User Guide
TransCore Proprietary
6-2
Communications Protocols
The AI1422E Reader supports the following communications protocols:
•
Basic
•
Error correcting protocol (ECP)
•
Data inquiry
The following protocol information provides reference information relevant to developing
host software.
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 within 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 capable of ignoring any messages that do not conform to the
som...eom frame sequence.
Both data mode and command mode require a two-way message interchange when
using ECP. This interchange is completed by the message recipient returning a message
acknowledgement to the message sender.
With ECP, all transmissions require a message. If a message is not received, the sender will
time out with the same effect as if it had received a negative acknowledgment (from the
host) or an Error message from the AI1422E Reader.
Software (XON/XOFF) flow control is optionally supported. Be careful in the use of XON/
XOFF since noise-induced characters may be interpreted by the AI1422E Reader as the
XOFF character, which would suspend reader output without information reaching the host
computer. For more information refer to
“525 Display Communications Protocol Status” on
page 7-17
.
Note: TransCore recommends that XON/XOFF flow control be disabled while using ECP.
Basic Protocol
With basic protocol, messages sent to and from the AI1422E Reader and the host are
transmitted without error checking. For each host transmission, the AI1422E Reader returns
a Done or Error message to the host.
When the host computer is physically close to the AI1422E Reader and no sources of
interference exist, the basic protocol provides reliable communications.
The host must be ready to receive reader-transmitted messages because in basic
protocol the AI1422E Reader does not wait for the host to acknowledge a message before
transmitting the next message. If necessary, the host may halt reader transmissions by
using software or hardware Refer to
“Command Codes” on page 7-2
for flow control
information.
Summary of Contents for 1422E
Page 16: ...Before You Begin 1...
Page 20: ...AI1422E Reader TransCore Proprietary 1 5...
Page 21: ...2 System Overview...
Page 25: ...AI1422E Reader TransCore Proprietary 2 5 Figure 2 2 Antenna to Tag Centerline Tolerance...
Page 26: ......
Page 27: ...3 Interface Connections...
Page 32: ...User Guide TransCore Proprietary 3 6...
Page 33: ...4 Installation Instructions...
Page 41: ...AI1422E Reader TransCore Proprietary 4 9...
Page 42: ...5 System Test Procedures...
Page 45: ......
Page 46: ...6 Communications Protocols...
Page 49: ......
Page 50: ...7 Command Codes...
Page 87: ...User Guide TransCore Proprietary 7 38...
Page 88: ...8 Troubleshooting and Maintenance...
Page 93: ......
Page 94: ...Character Conversion A...
Page 96: ...B Technical Specifications...
Page 99: ......
