7 Serial Communications
7 - 32
NX-series Communications Interface Units User’s Manual (W540)
If transmission buffering is enabled, the send data is sent to the serial line only after all of the send data
is passed from the CPU Unit or communications master to the CIF Unit.
Therefore, the data send time will be the total of time A and
time B in the following diagram.
For example, the data send times for various baud rate and I/O
refresh cycles are given in the following
table for these parameter values.
Data Send Times [ms]
Data Send Times When Transmission Buffering Is Enabled
Letter Definition
A The time from when the CPU Unit or communications master sta
rts sending the data to the CIF Unit
until the CIF Unit starts sending the data to the serial line
B 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
Divided data size [bytes]
*1
*1. Refer to 6-3 Setting the Divided Data Size on page 6-6 for the procedure to set divided data sizes.
20
Baud rate
[bps]
I/O refresh cycle [ms]
0.5 1 2 4
1,200 2,153 2,172 2,211 2,287
2,400 1,086 1,106 1,144 1,221
4,800 553 572 611 687
9,600 286 306 344 421
19,200 153 172 211 287
38,400 86 106 144 221
57,600 64 83 122 199
115,200 42 61 100 176
230,400 31 50 88 165
A
B
Send data sent from the
CPU Unit or communica-
tions master to the CIF Unit
The send data is sent to the serial line only after all of the send
data is passed from the CPU Unit or communications master to
the CIF Unit.
Send data on the
serial line
Data send time [ms] = A [ms] + B [ms]
I/O refresh cycle [ms] × Number of I/O refreshes × Output data size [bytes]
A [ms] =
Divided data size [bytes]
Bits per character
B [ms] = × Number of characters × 1,000
Baud rate [bps]
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