西门子博图ModbusRTU轮询FB

//==代码=
//PLC首次扫描时设置通讯模式
IF "FirstScan" THEN
#Modbus_Comm_Load_Instance.MODE := 4;
END_IF;
//复位错误
IF #Reset THEN
FOR #i := 0 TO 5 BY 1 DO
#Request[#i].Status := 16#0000;
END_FOR;
END_IF;

//初始化端口

Modbus_Comm_Load_Instance(REQ:="FirstScan" OR #Reset,

"PORT":=#Port,
BAUD:=#Baud,
PARITY:=#Parity,
FLOW_CTRL:=0,
RTS_ON_DLY:=0,
RTS_OFF_DLY:=0,
RESP_TO:=1000,
MB_DB:=#Modbus_Master_Instance.MB_DB);
//初始化完成
IF #Modbus_Comm_Load_Instance.DONE THEN
#Init_OK := TRUE;
END_IF;
//初始化失败
IF #Modbus_Comm_Load_Instance.ERROR THEN
#Retval := #Modbus_Comm_Load_Instance.STATUS;
RETURN; //退出功能块
END_IF;
//调用主站

Modbus_Master_Instance(REQ:=#Req,

MB_ADDR:=#Work.SlaveNO,
MODE:=#Work.Mode,
DATA_ADDR:=#Work."Data Address",
DATA_LEN:=#Work."Data Length",
DATA_PTR:=#Work.Result);

CASE #STEP OF
00://RUN需要保持
IF #Run AND NOT #Reset AND #Init_OK THEN
#STEP := 10;
END_IF;
10://限定循环范围，保持在数组的索引内
IF #Index < #Slave_1ST OR #Index > #Slave_Last THEN
#Index := #Slave_1ST;
#STEP := 20;
END_IF;
20://判断从站是否有错误，有则跳过
IF #Request[#Index].Status = 0 THEN
#STEP := 30;
ELSE
#STEP := 50;
END_IF;
30://启动主站的读写请求
#Work := #Request[#Index];
#Req := TRUE;
#STEP := 40;
40://接收从站的信息
IF #Modbus_Master_Instance.DONE OR #Modbus_Master_Instance.ERROR THEN
#Request[#Index].Result := #Work.Result;//保存读取到的信息
#Request[#Index].Status := #Work.Status;//保存从站的状态
#STEP := 50;
#Req := FALSE;
END_IF;
50:
#Index := #Index + 1;
#STEP := 00;
END_CASE;
````