Campbell SDM-SIO4, Instruction Manual

Page: 73 / 82

Section 6. Data Error Detection
6-11
6: SDM-SIO4 (P113)
1: 1 Reps
2: 0 Address
3: 1 Send/Receive Port 1
4: 2304 Command
5: 9102 1st Parameters
6: 0 2nd Parameters
7: 1 Values per Rep
8: 0000 Loc [ _________ ]
9: 1 Mult
10: 0 Offset
*Table 2 Program
02: 0.0 Execution Interval (seconds)
*Table 3 Subroutines
End Program
The string transmitted from port one might be ‘some 234.34FFFF’.
where FFFF would be the hex CRC16 for the string ‘some 234.34’.
FFFF is not the actual signature for the above string it is only an
example.
When the Checksum, CRC or Signature calculation is used it will increase any
delay required after initiating one P113 and before initiating the next. How
much extra time required will be dependent on which algorithm is used. The
timings for the algorithms are shown below. These timings are in addition to the
normal formatter delay times:
a
Time to set up an algorithm using formatter ‘g’ is No. of Ports*0.0656ms.
b
The time using the different algorithms is shown below. Note that this is the
time that is needed for each character that the formatter has to deal with, and so
this time would be multiplied by the total number of characters you expect to
transmit multiplied by the number of ports you are sending it to.
1,2 CRC16 and CRC16-CCITT 0.159ms/char.
3 CRC16-CCITT-IBM 0.159ms/char.
4 CRC32 0.369ms/char.
5 CSI Signature 0.077ms/char.
6 Checksum using modulo 256 0.066ms/char.
7 Checksum using modulo 8192 0.071ms/char.
c
The different data types are shown below. Note that this is the time needed to
convert the calculated signature into the correct format and must be multiplied
by the number of ports it is being sent to. The ASCII decimal conversion timing
NOTE