Siemens Simatic S7-300 CP 341 - RS 485 Mode

Basic Principles of Serial Data Transmission
2.6 Data Transmission with the ASCII Driver
CP 341 Point-to-Point Communication, Installation and Parameter Assignment
Manual, 09/2008, A5E02191071-01 71
2.6.4 RS 485 mode
RS 485 mode
When you run the ASCII driver in RS 485 mode (half-duplex, two-wire mode), you must take
steps in the user program to ensure that only one station sends data at any one time. If two
stations send data simultaneously, the message frame will be corrupted.
RS 232C accompanying signals
The following RS 232C accompanying signals are available on the CP 341 RS 232C:
● DCD (input) Data carrier detect;
Data carrier detected
● DTR (output) Data terminal ready;
CP 341 ready for operation
● DSR (input) Data set ready;
Communication partner ready for operation
● RTS (output) Request to send;
CP 341 ready to send
● CTS (input) Clear to send;
Communication partner can receive data from CP 341
(Response to RTS = ON of the CP 341)
● RI (input) Ring Indicator;
Ring Indicator
When the CP 341-RS 232C is switched on, the output signals are in the OFF state (inactive).
You can control the DTR/DSR and RTS/CTS control signals using the CP 341: Point-to-Point
Communication, Parameter Assignment parameter assignment interface or via functions
(FCs) in the user program.
Controlling RS 232C accompanying signals
The RS 232C accompanying signals can be controlled as follows:
● When automatic control of all RS 232C accompanying signals is assigned
● When data flow control (RTS/CTS) is assigned
● By means of the FC V24_STAT and FC V24_SET functions
Note
When automatic control of the RS 232C accompanying signals is assigned, neither
RTS/CTS data flow control nor RTS and DTR control by means of the FC V24_SET
function are possible. When RTS/CTS data flow control is assigned, RTS control by
means of the FC V24_SET function is not possible. On the other hand, it is always
possible to read all RS 232C accompanying signals by means of the FC V24_STAT
function.
The sections that follow describe the basic principles for controlling and evaluating RS 232C
accompanying signals.
该文档是极速PDF编辑器生成，
如果想去掉该提示,请访问并下载：
http://www.jisupdfeditor.com/
长沙工控帮教育科技有限公司
www.gkbpx.com