
TPU2000/2000R Modbus/Modbus Plus Automation Guide
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Carriage Return (One Character)
Each base transmitted and received command has at least 9 characters for transmission. The transmission time,
depending upon baud rate can range from 74.97 mS (at 1200 baud) to 4.689 mS (at 19200 baud). For example
Figure 5-14 illustrates the Function 01 Read Coil Status format. Figure 5-15 illustrates the transaction request for
four coils. Analysis of the data transmitted and received yields the following:
Transmission Request:
Common characters 9 + 4 address char 4 data request characters
Total characters for transmission request = 17 characters.
Returned Response
Common characters 9 + 2 data byte char 4 data returned characters.
Total characters returned by TPU2000/TPU2000R = 15 characters.
Depending upon the baud rate the total time for the communication characters to propagate along the network
could range from:
Transmission Request:
17 characters at 141.61. mS (1200 Baud) to 8.857 mS (19200 Baud)
Returned Response
15 characters at 124.95 mS (1200 Baud) to 7.815 (19200 Baud)
Total network transfer time via the physical medium can range from 265.56 mS at 1200 baud to 16.672 at 19,200
baud.
Baud rate is a major influence at 1200 baud and a lesser influence at 19200 baud. It must be realized that this is
only one of three components analyzed for a complete throughput analysis. In this case the Host time to
generate the command.
TPU2000/TPU2000R Throughput Analysis
Communication implementation within a protective relay is a demanding task. In other devices, communications
may take first priority. Within an ABB protective relay
PROTECTION IS THE FIRST PRIORITY.
Communication
shall not compromise protection capabilities. Thus communication throughput may vary depending upon the
demands of the protection. Table 5-86 illustrates the TPU2000/TPU2000R average benchmark times for
recognition of a Modbus command at the physical port and the time it takes to generate a reply to the respective
port. The times listed in the table are average times and do not include the calculated values generated in
Section 4.
Table 5-86. TPU2000/TPU2000R Modbus Command Throughput (Average Time in mS
)
Reading
from
TPU2000/TPU2000R
Write to
TPU2000/TPU2000R
MODBUS Command
Register
Start
Num. Refs. Min (ms) Max (ms) Min (ms) Max (ms)
Real Logical Outs
00001
14
5.023
14.417
Read Physical Outs
00129
4
1.497
10.688
Read Physical Inputs
10129
2
1.381
13.726
Load Metering
40513
27
21.270
30.184
Configuration & Status
40129
22
18.848
26.324