Siemens SIMATIC CP 440, Руководство пользователя

Страница: 37 / 172

Basic Principles of Serial Data Transmission
2-19
Point-to-point connection CP 440 Installation and Parameter Assignment
A5E00057742-02
The figure below illustrates a receive operation with the end criterion “fixed
message frame length”.
Waiting for
character
Character
arrived
Error when receiving
Message frame buf
fered
End criterion for message frame identified, error entry follows
Character received
with length control
and character delay
time
Message frame
entered in receive
buffer
Error entered in the
STATUS output of
the FB.
Waiting for
parameterized
number of
characters
Message
frame
complete
Expiration
of the
monitoring
time
Figure 2-7 Sequence of Receive Operation with End Criterion “Fixed Message Frame
Length”