ABB TPU2000 Technical Manual page 266

TPU2000/2000R Modbus/Modbus Plus/ Modbus TCP/IP Automation Guide
TR = (2.08 + 0.016 * 16) * 1 + (0.19 + 0.016 * 0 ) * 0 + (0.53 * 2)
TR = 2.336 + 0 + 1.06
TR = 3.239 mS
As per the suggestions in the manual, the worst case token rotation time is:
TR wk = 1* TR = 3.239 mS
As per the suggestions in the manual,the best case token rotation time is:
TR bk = 0.5 * TR = 1.620 mS
Let us assume that a single read is triggered by a physical input on the PLC transitioning from a level 0 to a level
1 on the PLC processor.
A PLC throughput analysis of the host yields the following:
PLC Input Delay = 1mS
PLC Scan = 4 mS per K: 2 scans of the PLC = 8 mS = 2 * 4 mS
PLC Scan and Delay = 5 mS best case and 9 mS worst Case
It is interesting to note that 32 words of Global Data (if used in this calculation) were requested. An additional
token rotation time of (32* 0.016) * 1 = 0.512 mS would be added to a token rotation worst case (0.256 average
contribution to the network otherwise). Thus with Global data, the average contribution for a single transaction
would be 1.024 mS worst case for each network transaction.
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