Campbell Hausfeld Serial I/O Interface SDM-SIO4 - Manual (Page 61)

Section 6. Data Error Detection
6-5
;if the value in location 1 is greater than zero then there must be data
;this assumes only one sensor is connected to the SDM-SIO4
7: IF (X<=>F) (P89)
1: 1 X Loc [ _________ ]
2: 3 >=
3: 1 F
4: 30 Then Do
;if data is available then get the value and put into location 2
8: SDM-SIO4 (P113)
1: 1 Reps
2: 0 Address
3: 1 Send/Receive Port 1
4: 4 Command
5: 0 1st Parameters
6: 0 2nd Parameters
7: 1 Values per Rep
8: 2 Loc [ _________ ]
9: 1 Mult
10: 0 Offset
;end of get data.
8: End (P95)
*Table 2 Program
02: 0.0000 Execution Interval (seconds)
*Table 3 Subroutines
End Program
The program shown above will only put data into the storage locations if any data
was available. Data being available is detected by polling the SDM-SIO4 to see if
any data is waiting. If you decided not to poll the SDM-SIO4 then you would get
-99999 in the locations if data was not available to collect.
When the Checksum, CRC or Signature calculation is used it will reduce the
speed at which the filters can deal with the data from the receive buffers. How
much slower the filters will be depends on which algorithm is used. The timings
for the algorithms are given below. These timings are in addition to the normal
filter processing times:
a
Time to set up an algorithm using filter “g” is 0.0656ms.
b
The time using the different checksum algorithms is shown below. Note that this
is the time that is needed for each character the filter has to deal with, and this
time would be multiplied by the number of characters you expect to receive while
the algorithm is being calculated. This factor would generally constitute the most
significant delay.