7 Serial Communications
7 - 4
NX-series Communications Interface Units User’s Manual (W540)
7-2 How Data Is Sent and Received
This section describes how the send and receive buffers in a CIF Unit are used to send and receive
data.
The definitions of the terms used for sending and receiving data are described in the following table.
When data is sent, the send data is first stored in the send buffer in
the CIF Unit, as shown in the follow-
ing figure, before the data is sent to the serial line. The send buffer size is 5,120 bytes per port.
The following procedure is used to send data.
1 In each I/O refresh cycle, the send data from the CPU Unit or communications master is sent in
order to the send buffer in the CIF Unit.
The size of send data that is transferred each time
depends on the divided data size setting. You
can change the divided data size to between 4 and 80 bytes. The default setting is 20 bytes.
2 The send data in the send buffer in the CIF Unit is sent to the serial line.
You can change the baud rate in the Unit oper
ation settings for the CIF Unit.
Term Meaning
Sending
data
Sending data from the Controller to the serial line.
Receiving
data
Receiving data from the serial line at the Controller.
Send data The data that is sent from the Controller to the serial line.
Receive
data
The data that is received by the Controller from the serial line.
7-2-1 How Data Is Sent
Receive buffer
Serial comm
cations devi
CPU Unit or
communications
master
CIF Unit
NX bus or
communica-
tions cable
Serial line
Send buffer
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