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7 Serial Communications
NX-series Communications Interface Units User’s Manual (W540)
7-8 Communications Performance
7
7-8-1 Calculating the Communications Performance
If transmission buffering is disabled, the first send data is immediately sent to the serial line after it is
passed from the CPU Unit or communications master to the CIF Unit.
Therefore, the data send time will
be the total of time C and time D in the following diagram.
For example, the data send times for various baud rate and I/O re
fresh cycles are given in the following
table for these parameter values.
Data Send Times [ms]
Data Send Times When Transmission Buffering Is Disabled
Letter Definition
C The time from when the CPU Unit or communications master starts sending the data to the CIF Unit
until the CIF Unit starts sending the data to the serial line
D The time from when the CIF Unit starts sending the data to
the serial line until sending is completed
Parameter Value
Number of I/O refreshes Always 3
Bits per character 10
Output data size [bytes] 256
Baud rate
[bps]
I/O refresh cycle [ms]
0.5 1 2 4
1,200 2,135 2,137 2,140 2,146
2,400 1,069 1,070 1,073 1,079
4,800 535 537 540 546
9,600 269 270 273 279
19,200 135 137 140 146
38,400 69 70 73 79
57,600 46 48 51 57
115,200 24 26 29 35
230,400 13 15 18 24
C
D
Send data sent from the
CPU Unit or communications
master to the CIF Unit
Send data on the
serial line
The first send data is immediately sent to the serial line after it is
passed from the CPU Unit or communications master to the CIF Unit.
Data send time [ms] = C [ms] + D [ms]
C [ms] = I/O refresh cycle [ms] × Number of I/O refreshes
Bits per character
D [ms] = × Number of characters × 1,000
Baud rate [bps]
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