TransCore AI1422E, User Manual

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Note: The AI1422E Reader transmits ID codes to the host computer when the AI1422E Reader is in
Data Mode. If the AI1422E Reader remains in Command Mode with tags passing through the read
zone, no tag IDs are reported.
Asynchronous Interrogator Data Message
The interrogator sends the transponder ID in 8-bit ASCII. The message format is as follows:
<7EH><7EH><01H><transponder count><transponder ID><CRC>
The interrogator transmits the most significant bit first. The CRC is calculated, starting with the most
significant byte.
No Response is received with the
~~CC
and
!01
commands.
Table 2 presents the field descriptions.
Table 2 Asynchronous Interrogator Tag Data Message Fields
Field Description Hex ASCII
Start of Message
These two bytes, along with the Message
type byte, designate the start of the data
message.
7E7E ~~
Message Type
An 01H indicates that this message is a tag
data message.
01 SOH
Transponder Seen
Count
After power-up, this 8-bit count begins with
01 and is updated each time a tag with a
unique ID moves out of the RF field, then
back into the RF field. This field is useful in
determining whether a train has multiple tag
reads of a given ID due to a change in the
train’s direction.
00 - FF N/A
Transponder ID
The data that is programmed into
the transponder. The data within the
transponder is 6-bit ASCII but the
interrogator translates this data into
standard 8-bit ASCII.
Hex ID ID
Cyclical Redundancy
Check
An 8-bit cyclical redundancy check
(CRC). Includes the Start of Header, the
Seen Count and the Transponder ID.
Refer to Appendix E on page E–84 for a
description of the CRC algorithm. There
is no carriage return or line feed for this
message.
00 - FF N/A
AI1422E Reader User Guide
TransCore Proprietary 6–22