Rockwell Automation 5370 Color CVIM Communications Manual - Manual (Page 105)

Chapter 5
Using the RS–232 Ports
5–37
To transmit the data value 10 hex, you must use the data code DLE DLE.
However, only one of these DLE data bytes is included in the BCC sum. For
example, to transmit the values 8, 9, 6, 0, 10, 4, and 3 hex, you would use the
following message codes:
Represents single
data byte value of 10
10 02 08 09 06 00 10 10 04 03 10 03 D2
DLE STX Data DLE ETX BCC
In this case, the sum of the data bytes is 2E hex because only one DLE text
code is included in the BCC. So the BCC is D2 hex.
The BCC algorithm provides a medium level of data security. It cannot
detect transposition of bytes during transmission of a packet. It also cannot
detect the insertion or deletion of data values of zero within a packet.
Use the deactivate force command to return outputs on the 2801–JMB local
I/O board to the Color CVIM module assigned functions. The deactivate
forces command is:
If the BCC is not valid, the Color CVIM module will respond with a DLE
NAK and the command will not be executed.
If the BCC is valid, the Color CVIM module will respond with a DLE ACK.
Then the Color CVIM module will validate the command structure. If the
command is valid, the Color CVIM module will execute the command and
return the data. If the command structure is invalid, the Color CVIM module
will not execute the command or respond.
Block Check Character
(cont’d)
Deactivate Forces