Поправил ошибки (выделил исправления жирным).

Код:
IF EnableRead THEN

   CASE ReadState OF

       STATE_MB_RD.CONNECTING:

       fbTcpClient
       (
         xEnable := TRUE ,
         tTimeout := T#5S,
         sIpAddr := '192.168.0.7',
         uiPort :=502
       );

      IF fbTcpClient.xActive THEN

         fbReadRequest (xExecute := FALSE);
         ReadState := STATE_MB_RD.READ;

      ELSIF fbTcpClient.xError THEN

         fbTcpClient(xEnable := FALSE);
         ReadState := STATE_MB_RD.CONNECTING;

      END_IF

   STATE_MB_RD.READ:

        fbReadRequest
        (
             xExecute:=TRUE,
             tTimeout:=T#5S,
             usiRetry:=5,
             hConnection:=fbTcpClient.hConnection,
             xIsRtuOverTcpMode:=FALSE,
             usiUnitId:=1,
             eFuncCode:=OCL.MB_FC.READ_INPUT_REGISTERS,
             uiDataAddr:=1,
             uiDataCount:=32,
             pData:=ADR (DatafORFANK),
             szSize:=SIZEOF (DatafORFANK)
         );

	IF fbReadRequest.xDone OR fbReadRequest.xError THEN
		
		EnableRead:=FALSE;
		ReadState := STATE_MB_RD.CONNECTING;
	
	END_IF

   END_CASE

END_IF
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