4 469 MOTOR MANAGEMENT RELAY – COMMUNICATIONS GUIDE
MODBUS PROTOCOL COMMUNICATIONS GUIDE
5. j + 1 --> j
6. shr (A)
7. Is there a carry?No: go to step 8.
Yes: G (+) A --> A and continue.
8. Is j = 8? No: go to 5.
Yes: continue.
9. i + 1 --> i
10.Is i = N? No: go to 3.
Yes: continue.
11.A --> CRC
Timing
Data packet synchronization is maintained by timing constraints. The receiving device
must measure the time between the reception of characters. If three and one half
character times elapse without a new character or completion of the packet, then the
communication link must be reset (i.e. all slaves start listening for a new transmission from
the master). Thus at 9600 baud a delay of greater than 3.5 × 1 / 9600 × 10 = 3.65 ms will
cause the communication link to be reset.
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