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Application Tag Commands

114 Command Set

Get Tag EPCs

When you want to get the tag EPCs out of the buffer and don’t care about the tag read

metadata, the options available with this syntax maybe useful. This syntax reads out the

requested number of tags from the buffer. A maximum of 13 tags are read at a time, less

if Max EPC Length is set to 496 bits. Multiple Get Tag Buffer commands may be required

to obtain the complete results from a single Read Tag Multiple command. If more tags

are requested than remain in the buffer an error will be returned.

All tag buffer indexes are encoded as 16-bit unsigned integers. The indexes start

counting from 0. Thus, a start index of 0 indicates tag #1, and a start index of 10 would

indicate tag #11.

There are two ways to read tag EPCs out of the buffer when you only want EPC values.

The first way is to send a Get Tag Buffer command with the desired number of tags, n.

This retrieves the next n tags, starting from the current read index. In the previous

example, the read index was 1, indicating that one tag was already read. To read the next

two tags, set the number of tags parameters to 2. This returns tags number 2 and 3 in the

tag buffer:

When using the Get Tag Buffer command in this way, the read index is automatically

incremented internally. Thus, if the read index was ‘1’ before getting two tags, then it is

incremented to ‘3’ at the end of this command.

Another way to get the second and third tags is to explicitly send the start and end

indexes of the tags to read. This is used to retrieve any contiguous block of tag buffer

entries at any time.

Using the start and end index method does not affect the read index that is internally

stored in the module. The above request returns a message with two tags. The length of

each tag EPC record returned is defined based on the max EPC length configured with

et Reader Configuration(9Ah), regardless of the size of a specific tag’s EPC. The sizes

and fields of the EPC portion of a tag buffer entry is defined in the Tag Buffer Entry

table.

For example:

FF 02 29 00 02 57 EB

SOH Length OpCode # Tag IDs to Return CRC

FF 04 29 00 01 00 03 CC 94

SOH Length OpCode Start Idx End Idx CRC