User's Manual

COBALT UHF-SERIES CHAPTER 5: COMMAND PROTOCOLS
PAGE 53 OF 140
5.4.3 ABx Fast – Command Packet Elements
Command Size
The ABx Fast protocol requires that the byte count, known as the Command Size,
be specified as a two-byte integer within each command packet. To calculate the
Command Size, add the total number of bytes within the command packet while
excluding the two byte Command Header, the two byte Command Size, the one byte
Checksum (if present) and the one byte Command Terminator (see example below).
COMMAND PACKET
ELEMENT
# OF BYTES INCLUDED IN COMMAND
SIZE?
Command Header 2 No
Command Size 2 No
Command ID 1 Yes
Start Address 2 Yes
Read/Block Size 2 Yes
Timeout Value 2 Yes
Additional Data Bytes 1 Yes
(if present)
Checksum 1 No
Command Terminator 1 No
Table 5-7: ABx Fast - Command Size Parameter
In the above sample command packet, there are eight bytes of data (located
between the Command Size parameter and the Checksum parameter) that are
included in the Command Size. Therefore, the Command Size for this example is
0x0008.
Command ID
The one-byte Command ID parameter identifies the Hex value of the RFID
command to perform. (See the Section 5.2 - ABx Fast RFID Command Table
.)
Start Address
The Start Address parameter holds a two-byte integer representing the tag memory
address location where a read or write operation is to begin.
Block Size (Read/Write Length)
The two-byte Block Size parameter (which is also sometimes called the Read /
Write Length parameter) indicates the number of bytes that are to be read from or
written to the RFID tag.
Command
Size =
number of
bytes in these
fields