User's Manual

Table Of Contents
ABxS Command 85 (85H): Block Read All
DESCRIPTION
Read a block of data from all RFID tags-in-field or those with the specified
Family ID.
DISCUSSION
This command is used to read segments of data from contiguous areas of tag
memory. It is capable of handling up to 48 bytes of data transferred to the
host with one command. The timeout value is given in 1 msec increments
and can have a value of 1EH to FFFEH (65,534 ms). When the timeout is
set to 0, the LRP820 will return a syntax error message 21H.
The Block Read All consists of Tag Family ID and an Anticollision Index, a
start address and length, followed by a timeout value and the message termi
-
nator, FFFFH. If the read length exceeds the last tag address, the LRP820
will return a syntax error message 21H.
The data read from the tag is returned in the LSB of the register, and the
MSB is always 00H.
A special termination packet (AAH FFH) is sent after the timeout expires.
When the Anticollision Index is not zero (multiple tag-in-field enabled), the
LRP820 will return a response after the timeout expires. If the Anticollision
Index is 0, the command returns a response after the successful operation on
one tag or when the timeout expires. No termination packet is sent when the
Anticollision Index is set to 0.
Field Remarks
Command Command number in hex preceded by AAH
Tag Family Tag Family ID - 00H = all tags
Anticollision index Number of tags expected in field
Start Address The tag address where the read will start
Read Length The number of tag addresses to be read
Timeout Timeout value given in 1 ms units (1EH - FFFEH)
Message Terminator FFFFH
NOTE:
This command can not be used over a MUX32 interface.
Copyright © 2000 Escort Memory Systems
66 LRP820-Series Long-Range Passive Reader/Writer