User's Manual

COBALT UHF-SERIES CHAPTER 5: COMMAND PROTOCOLS
PAGE 54 OF 140
Timeout Value
Most ABx Fast commands include a two-byte Timeout Value, which is used to limit
the length of time that the Cobalt UHF will attempt to complete the specified
operation.
The Timeout Value is measured in 1-millisecond increments and has a maximum
supported value of 0xFFFE or 65,534 milliseconds (which is slightly longer than one
minute).
Setting a long Timeout Value does not necessarily mean that a command will take
any longer to execute. This value only represents the period of time for which the
Cobalt UHF will attempt execution of the command.
IMPORTANT:
During write commands, the tag must remain within the antenna’s RF field until the
write operation completes successfully, or until the Timeout Value has expired.
If a write operation is not completed before the tag leaves the controller’s RF field, data
may be incompletely written.
Checksum
The ABx Fast Command Protocol supports the inclusion of an optional Checksum
byte that is used to verify the integrity of data being transmitted between host and
controller.
The Checksum is calculated by adding together (summing) the byte values in the
command packet (less the Command Header, Checksum and Command Terminator
parameters), and then subtracting the total byte sum from 0xFF.
Therefore, when the byte values of each parameter (from Command Size to
Checksum) are added together, the byte value sum will equal 0xFF.