SWISS PLUS RT100V8BT, Руководство пользователя

Страница: 14 / 37

14
Description of the frame transmitted each time a transponder is read
The PetScan transmits the following frame to the PC after each valid reading :
Octet at the start of
the
frame : ″U″ ″/x55″
Type of 8
character
(or octet)
chip
The 16
character
(or octet)
chip
identifier
Separation
of
octet: ″*″:
CRC-CCITT-control
word, 16 ASCII format
bits on 4 characters
Carriage
Return
octet: ″/x0D″
Tips: the developers of software associated with PetScan must use the head and separation characters to separate
the information transmitted by PetScan, calculate a control word with the data received and compare it to the word
transmitted by the PetScan to validate the information (see appendix for the CRC-CCITT-16 bit calculation
algorithm)
Description of the frames emitted when reading the databases (PetSCAN memory option)
If a PetScan reader has a memory option, when « Press SCAN to send » is displayed, the reader is ready to transmit
the identifiers stored in the memory. The PetScan displays « Sending ! » during transmission and the reader offers
the user the option of deleting the content of its database at the end of the transmission.
Format of the frames transmitted to the PC : the frame which is transmitted on each reading of a transponder is
preceded by a header octet ″/xAA″, its 4 character registration number in the memory and a separation
character ″*″.
Algorithm for calculating aCRC-CCITT-16bit control word
The C ANSI function’s source code enabling a control word to be calculated from a string of characters terminating
with
the character ″/x00″ is described below. The JAVA applet on the
« http://www.zorc.breitbandkatze.de/crc.html », website enables you to also calculate the control word.
Previously the fields had to be correctly completed before making the CRC calculation and a check made that the
control word is equal to 0xE5CC or the ″123456789″ character string.
Start of
frame
octet : ″/
xAA″
4 character
registration
number
Separation
octet: ″*″
Start of
information
object : ″U″
″/x55″
The type
of 8
character
(or octet)
chip)
The 16
character
(or octet)
chip
identifier)
Separati
on of
octet: ″*
″:
CRC-CCITT-cont
rol word, 16
ASCII format bits
on 4 characters
Carriage
return
octet: ″/x
0D″
Data used to calculate the CRC
Data used to calculate the CRC