Basic Principles of Serial Data Transmission
2.5 Data transfer using the ASCII driver
PtP coupling and configuration of CP 340
50 Manual, 04/2011, A5E00369892-03
2.5.2 Sending Data with the ASCII Driver
Sending
When sending data, specify the number of bytes of user data to be transmitted as the "LEN"
parameter when you call the P_SEND function block. The user data must contain any
required start-of-text and end-of-text characters.
If you are working with the end criterion "character delay time expired" when receiving data,
the ASCII driver will pause between two frames, even when sending. You can call the
P_SEND FB at any time, but the ASCII driver does not begin its output until a period longer
than the parameterized character delay time has elapsed since the last frame was sent.
Note
When XON/XOFF flow control is parameterized, the user data must not contain the
parameterized XON or XOFF characters. The default settings are
DC1 = 11H for XON and DC3 = 13H for XOFF.
Sending data
The figure below illustrates a send operation.
:DLWLQJIRU
VHQGUHTXHVW
6HQGLQJXVHU
GDWD
7KHDPRXQWRIGDWDWR
EHVHQWLVWDNHQIURP
WKH/(1SDUDPHWHURI
WKH3B6(1')%
5HTXHVWSURFHVVHG
6HQGUHTXHVWDUULYHG
Figure 2-14 Flowchart of a send operation
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