User Manual

CHAPTER 6: COMMAND PROTOCOLS
COBALT HF RFID CONTROLLERS OPERATOR’S MANUAL
P/N: 17-1320 REV 01 (03-06) PAGE 63 OF 116
6.2.4 ABx Fast - Command Packet Parameters
C OMMAND S IZE
The ABx Fast protocol requires that the byte count, known as the
Command Size
, be
specified as a 2-byte integer. To calculate Command Size, add the total number of bytes
within the command packet while excluding the two bytes for the Header, the two bytes
for the Command Size, the one byte for the Checksum (if present) and the one byte for
the Terminator (see example below).
PACKET
PARAMETER
# OF
BYTES
INCLUDED IN
COMMAND SIZE?
Header
2 No
Command Size
2 No
Command ID
1 Yes
Start Address
2 Yes
Read/Write Length
2 Yes
Timeout Value
2 Yes
Additional Data Bytes
1 Yes
Checksum
1 No
Terminator
1 No
In the above command packet example, 8 bytes of data are located between the
Command Size parameter and the Checksum parameter. Therefore, the Command Size
for this example is 0x0008.
S
TART A DDRESS
The Start Address parameter is holds a two-byte integer representing the tag memory
address location where a read or write operation will begin.
R
EAD/WRITE L ENGTH
The two-byte 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