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Chapter 4 Macro Function|ScrEdit Software User Manual
Revision Apr. 30th, 2007, 2007PDD23000002 4-35
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.
No Flow Control
Flow control function is disabled.
CTS/RTS
It is 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 connecting cable.
DSR/DTR
It is flow control for hardware also. It is used when PC and HMI is connected by cable directly.
XON/XOFF
It is flow control for software. It is only used for 2400bps modem. The control method is to generate
control code by software and add it in the transmission data.
Fig. 4.3.10 Flow control
ADDSUM
ADDSUM → It uses addition to calculate checksum.
V1=ADDSUM(V2, V3). V1 is the value after calculation, V2 is the starting address for calculation and
V3 is data length.
XORSUM
XORSUM → It uses XOR to calculate checksum.
V1=XORSUM (V2, V3). V1 is the value after calculation, V2 is the starting address for calculation and
V3 is data length.
PUTCHARS
PUTCHARS → Output characters by COM port.
V1= PUTCHARS (V2, V3, V4). V1 is the response value after communication. If the communication has
succeeded, the result will be stored in $1. If the communication has failed, the result will be stored in $0.
V2 is the starting address of transmission data, V3 is data length, and V4 is the maximum allowable
communication time and its unit is ms.