Chapter 3 Creating and Editing Screens
No Flow Control: Flow control function is disabled.
Flow Control: The transmission speed and communication validity are enhanced during
communication due to new transmission technology, such as compress immediately,
debug,…etc. But the new technology also makes the transmission speed between HMI
and PC will be longer than the actual transmission speed. Therefore, ensure the data
security and transmit complete data between computer and HMI, when transmitting data
through serial communication port, the flow control is necessary.
To make sure that data transmit between computer and HMI is completed, the user can
use Flow Control functions.
CTS / RTS: Flow control for hardware. It uses handshaking signal to control receiving
and sending data. The control is achieved via internal modem or external modem
that connects to HMI by a connecting cable.
DSR / DTR: Flow control for hardware also. It is used when PC and HMI are connected
directly by a cable.
XON / XOFF: Flow control for software. Only used for 2400bps modem. The control
method is to generate control code by software and add it in the transmission data.
Example
When the communication protocol is set to COM1, RS232, 7, Even, 1, 9600, and No
Flow Control, if the response value is stored in $0, the user’s screen will look like the
following figure.
Equation
Var1 = ADDSUM (Var2, Var3)
Explanation
This command uses addition to calculate checksum. Var1 is the value after
calculation, Var2 is the starting address for calculation and Var3 is data length.
3-356 Revision May, 2010