ThingMagic Micro Hardware - Manual (Page 64)

Tag Handling
A D I V I S I O N O F T R I M B L E
Functionality of the Micro 59
Tag Handling
When the Micro performs inventory operations (MercuryAPI Read commands) data is
stored in a
Tag Buffer until retrieved by the client application, or streamed directly to the
client if operating in Tag Streaming/Continuous Reading mode.
Tag Buffer
The Micro uses a dynamic buffer that depends on EPC length and quantity of data read.
As a rule of thumb it can store a maximum of 1024 96-bit EPC tags in the TagBuffer at a
time. Since the Micro supports streaming of read results the buffer limit is, typically, not an
issue. Each tag entry consists of a variable number of bytes and consists of the following
fields:
The Tag buffer acts as a First In First Out (FIFO) — the first Tag found by the reader is
the first one to be read out.
Tag Streaming/Continuous Reading
When reading tags during asynchronous inventory operations (MercuryAPI
Reader.StartReading()) using an /reader/read/asyncOffTime=0 the Micro “streams”
the tag results back to the host processor. This means that tags are pushed out of the
buffer as soon as they are processed by the Micro and put into the buffer. The buffer is
put into a circular mode that keeps the buffer from filling. This allows for the Micro to
perform continuous search operations without the need to periodically stop reading and
fetch the contents of the buffer. Aside from not seeing “down time” when performing a
read operation this behavior is essentially invisible to the user as all tag handling is done
by the MercuryAPI.
Total Entry
Size
Field Size Description
68 bytes
(Max EPC
Length = 496bits) EPC
Length 2 bytes Indicates the actual EPC length of the tag
read.
PC Word 2 bytes Contains the Protocol Control bits for the tag.
EPC 62 bytes Contains the tag’s EPC value.
Tag CRC 2 bytes The tag’s CRC.
Tag Read Meta Data