LSIS XBE-DC08A, Руководство пользователя, Страница: 1035 / 1284

Chapter 2 Built-in Cnet communication
2-37
B
u
ilt
-in
C
omm
a) BCC error check
When BCC is applied, calculation about TRX frame is executed and if calculation is different, relevant frame is
ignored to improve the reliability of communication. Calculation methods about each BCC are as follows.
Classification BCC method Contents description
General
method
checking error
Byte SUM Adds designated data as I byte unit and uses lower byte value
Word SUM Adds designated data as 1 word unit and uses lower word value
Byte XOR
Executes Exclusive OR calculation about designated data as 1 byte
unit and uses lower byte
7bit SUM Uses result value of byte sum except the most significant bit
7bit XOR Uses result value of byte XOR except the most significant bit
7bit SUM#1 If result of 7 bit SUM is less than 20
H,
it adds 20
H.
Byte SUM 2’S COMP Takes 2’s complement about byte sum result
Byte SUM 1’S COMP Takes 1’s complement about byte sum result
CRC 16 16 bit error detection method
CRC 16 IBM 16 bit IBM CRC error detection method
CRC 16 CCITT 16 bit CCITT CRC error detection method
MODBUS LRC MODBUS LRC error detection method
Method
checking error
for dedicated
communication
LGIS CRC Error detection method used for LSIS PLC
DLE AB Error detection method used for DF1Protocol of Allen Bradley
DLE SIEMENS Error detection method used for Siemens 3964R communication
When setting BCC, in case of general method, the user need not set BCC setting range and indication method and
in case of dedicated method, the user should set BCC setting range and indication method.
Item Contents
Start
position
Start area Determines where BCC calculation starts from among HEAD/BODY/TAIL
Segment
Determines segment location to start BCC calculation in HEAD/BODY/TAIL. 0 means first segment will be
included in the BCC calculation
End
position
Before BCC Included from start position to before BCC
End of area Included from start position to end of designated area
Settings Included from start position to designated area segment
ASCII conversion Converts result value, its size will be double
Initial value 0
Designates BCC initial value as 0. If there is no designation, initial value is FF
H.