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6 . 2 . 4
A B x F a s t - C o m m a n d P a c k e t P a r a m e t e r s
C o m m a n d S i z e
The ABx Fast protocol requires that the byte count, known as the Command Size,
be specified as a two-byte integer. To calculate the command size, add the total
number of bytes within the command packet while excluding the header, command
size, checksum (if present) and terminator (see example below).
Command
Size =
number of
bytes in these
fields
The command size for this example is 0x0008.
S t a rt A d dre ss
The Start Address parameter holds a two-byte integer representing the tag memory
address location where a read or write operation will begin.
Re ad /W r ite Le ngt h
The two-byte Read/Write Length integer indicates the number of bytes that are to be
read from or written to the RFID tag.
T i m eo ut Va l ue
A two-byte Timeout Value parameter (measured in one-millisecond increments) is
used to set the length of time that the controller will attempt to complete the specified
operation.
The maximum supported timeout value is 0xFFFE or 65,534ms (slightly longer than
one minute). Setting a long timeout length does not necessarily mean that a
command will take any longer to execute. This value only represents the period of
time for which the controller will attempt to complete 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.
C 0 4 0 5 - X X X - 0 1 O P E R A T O R ' S M A N U A L – R E V . 0 3
C O M M A N D E L E M E N T
Command Header
Command Size
Command ID
Start Address
Read/Write Length
Timeout Value
Additional Data Bytes
Checksum
Command Terminator
C H A P T E R 6 : C O M M A N D P R O T O C O L S
# O F B Y T E S
I N C L U D E D I N
C O M M A N D S I Z E ?
2
No
2
No
1
Yes
2
Yes
2
Yes
2
Yes
1
Yes
1
No
1
No
P A G E 5 6 O F 7 5
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