The communication port of the EVE Automation UN200 CPU can be set to free port mode. When free port mode is selected, the user program has complete control over the operation of the communication port, and the communication protocol is also entirely under the control of the user program. When the S7-200 CPU is in free port communication mode, the communication function is completely controlled by the user program; all communication tasks and information definitions must be implemented by the user program.
Free-port communication: As the name suggests, it is very flexible and can be controlled flexibly through user programs, without a fixed mode. Below, we will introduce the steps and methods of free-port programming and the usage of XMT and RCV instructions through an example of communication between the UN200 CPU and the UT500 high-performance vector inverter. Programming steps: 1. First, understand the message format of the communication object . Strictly follow the message format of the other device when programming. The message format of the Yiwei Automation UT500 inverter is as follows: Read function code: 03H. The UT500 can read a maximum of 5 consecutive data entries. For example, to read inverter 2100H (hexadecimal address), reading 3 consecutive words will produce the following host command information: Write function code: 06H, writes data into the UT500 frequency converter to modify the frequency converter's parameter values. For example, write 1388H (hexadecimal) into address 3000H (hexadecimal). 2. Initialize Communication Parameters: 1) Define the free port mode, baud rate, and data format for SMB30 (PORT0) and SMB130 (PORT1). 2) Define the communication port receiving formats SMB87 (PORT0) and SMB187 (PORT1), including the start and end information reception methods. 3) Set the start bit to SMB88 or SMB188, the stop bit to SMB89 or SMB189, and the maximum number of characters that SMB can receive to SMB94 or SMB198. 4) If using interrupts, connect the interrupt event and enable the interrupt ENI. 5) Set the communication parameters for the third-party device UT500 inverter, using PORT0 or PORT1 ports 3 and 8 directly connected to the A+ and B- communication terminals of the UT500 inverter. 3. Programming: For ease of understanding, we will program separately for sending XMT and receiving RCV commands below. Sending: Based on the communication format of the UT500 frequency converter, write data 1388H (50.00HZ in hexadecimal) into the address of the given frequency 3000H (hexadecimal) of the UT500 frequency converter. The sending program is written as follows: Main program OB1: CRC subroutine: According to the communication format of the UT500 frequency inverter, the data is read from the address 0C01H (hexadecimal) of the given frequency of the UT500 frequency inverter. The received data is placed into the first byte of VB200. The receiving program is written as follows: Main program OB1: CRC Subroutine: Interrupt 0 (INT0) Program: Interrupt 1 (INT1) Program: The above programs verify that the free port can communicate normally with the UT500 frequency converter. We believe you now have a basic understanding of free port communication. Try it yourself and see how it communicates with other intelligent devices using the UN200 PLC. (Forwarding code: Yiwei Company Philosophy: Established by Quality, Winning with Heart) Yiwei Automation Technology Co., Ltd.'s UT500 frequency converter can also perform MODBUS communication via MODBUS instruction library files and DP communication via an extended DP card. Welcome to follow Yiwei's WeChat subscription account for the latest industrial control technology!Read next
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