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113 LRP2000 Passive Reader/Writer
6.5.17 ABxF Command 8DH: Stop/Start Continuous Read All
DESCRIPTION
Command 8DH starts and stops continuous read mode for multiple tags.
DISCUSSION
The Start/Stop Continuous Read All mode is initiated by issuing the command with the Number of Bytes
set to any valid nonzero value. Stop the mode by sending the command with a read length of 0. While in
this mode, any other command can be issued and will be handled properly. After processing the new
command, the controller resumes the Continuous Read All mode.
The command has a parameter, Tag Repeat Count, that can prevent multiple reads of the same tag. A tag
is not read a second time until a specified number of tags have been read since the tag was last read.
Allowed values are from 0 up to 255 (FFH), where 0 means the tag can be re-read anytime. When
Continuous Read All mode is interrupted with other commands, the tag delay count is cleared during
execution of the other commands and then resumed. When the continuous read mode resumes, all
previously read tags will be read again. The controller responds with an acknowledge packet followed by
data packets for each tag read. The CONFIG LED blinks after each packet transmission.
Example
Reads four bytes of data from the tag starting at address 0001H. The Family ID byte is set to zero, so all
tags are read. The tag repeat count is set to 20 (14H). Two tags respond with read data.
Field Content
Header 0202H
Command Size Command length in bytes excluding the header command size, checksum, and terminator bytes.
Command 8DH
Family ID Tag Family ID - 00H = all tags
Reserved Ignored byte, set to 00H
Start Address Tag address for the start of the read
Number of Bytes 0 = stop. Any valid nonzero value indicates the number of bytes to be read
Tag Repeat Count Number of tags that must be read before the same tag is read again (0-255)
Checksum Optional checksum
Message Terminator 03H
Command from Host Response from Controller
Field Content Field Content
Header 0202H Header 0202H
Command Size 0008H Response Size 0001H
Command Code 8DH Command Echo 8DH
Family ID 00H Checksum 71H
Reserved 00H Terminator 03H
Start Address 0001H
Read Length 0004H
Tag Repeat Count 14H
Checksum 50H
Terminator 03H