Transmission Integrity - Siemens SIMATIC CP 340 User Manual

Basic Principles of Serial Data Transmission

2.3 Transmission integrity

2.3 Transmission integrity
Introduction
Transmission integrity plays an important role in the transmission of data and in selection of
the transmission procedure. Generally speaking, the more layers of the reference model are
applied, the greater the transmission integrity.
Classifying the Supplied Protocols
The CP 340 governs the following protocols:
● 3964(R) procedure
● ASCII driver
● Printer Driver
The figure below illustrates how these supplied protocols of the CP 340 fit into the ISO
reference model:
Figure 2-4
Transmission Integrity with the Printer Driver
Data Integrity When Using the Printer Driver:
● No data integrity precautions are taken for data transmission with the printer driver.
● To prevent data from being lost in the event of the printer receive buffer overflowing, you
● When data is output to the printer, the printer's BUSY signal is evaluated. The CP 340
30
Position of the Supplied Protocols of the CP 340 in the ISO Reference Model
can work with data flow control (XON/XOFF, RTS/CTS).
receives the BUSY signal as a CTS signal and evaluates it in the same way (see ASCII
driver). Please note that, when using CTS/RTS flow control, you must set the polarity of
the BUSY signal to CTS = "OFF" on the printer.
PtP coupling and configuration of CP 340
Manual, 04/2011, A5E00369892-03