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LRP2000 Passive Reader/Writer
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6.4.5 ABxS Command 08H: Tag Search
DESCRIPTION
Check to see if there is an RFID tag in the antenna field.
DISCUSSION
This command activates the controller to search for the presence of a tag within range of the antenna. If
the controller finds a tag, it returns a command echo to the host. The timeout value is given in 1 ms
increments and can have a value of 001EH to FFFEH (30 to 65,534 ms). When the timeout is set to 0, the
controller returns a syntax error. If no tag is present, it returns an error message. See Section 6.2 for more
information on error codes.
Example
Checks for an RFID tag in the RF field. A timeout of 2 seconds (07D0H = 2000 x 1 ms increments) is set for
the completion of the Tag Search.
6.4.6 ABxS Command 0DH: Stop/Start Continuous Read
DESCRIPTION
When in Continuous Read mode, the controller sends read commands continuously to any tag in range of
the antenna. When a tag comes within range, it is read and the data passed to the host computer. The
controller continues to read the tag but does not send the same data to the host until the tag has been
outside the RF field for a specified time period. This Delay Between Identical Decodes parameter prevents
redundant data transmissions when the controller is in Continuous Read mode.
DISCUSSION
The Start/Stop Continuous Read command contains three parameters: read length, start address, and
delay between identical decodes. The read length parameter switches the mode. Any valid, non-zero
length (1-48) sets the controller into Continuous Read mode. A read length value of 00H turns Continuous
Mode off. The Delay Between Identical Decodes parameters can have a value of 0 to 60 seconds. When
the Delay Between Identical Decodes is set to 0, the controller continuously reads AND transmits tag data
to the host. This can flood the buffers and cause communication errors and data loss. If the controller
receives other commands from the host, it executes them and then resumes Continuous Read mode. To
exit Continuous Read mode, issue the command with a read length of 0.
Field Remarks
Command Command number in hex preceded by AAH
Timeout Timeout value given in 1 ms units (001EH - FFFEH)
Message Terminator FFFFH
Command from Host Response from Controller
MSB LSB Remarks MSB LSB Remarks
AAH 08H Perform Command 8 AAH 08H Command Echo
07H D0H 2-second Timeout FFH FFH Message Terminator
FFH FFH Message Terminator