It has the same purpose as ReadRefresh, but while ReadRefresh performs actual communication when ReadRefresh is called, ReadRequest does not perform actual communication at the time of calling, and instead processes all the read requests accumulated by the ReadRequest calls up to that point when ReadRequestRefresh is called. In addition, requests added with the ReadRequest method are cleared by calling the ReadRequestRefresh method regardless of whether the processing was successful or unsuccessful. If you want to retry when a request fails, call the ReadRequest method again to make the request and then call the ReadRequestRefresh method.

ReadRefresh allows you to specify multiple tags at once as a string array. When reading the values of multiple tags, calling ReadRefresh once will result in faster processing than calling it multiple times.

this.ReadRequest ("$D0");
this.ReadRequest ("$D1");
this.ReadRequest ("$D2");
this.ReadRequestRefresh("device");

If you want to perform a retry using ReadRequestRefresh, you must call the ReadRequest method again.

::ReadRequest("U01.F01.T01");
::ReadRequest("U01.F01.T02");
if (::ReadRequestRefresh() == F)
{
  ::ReadRequest("U01.F01.T01");
  ::ReadRequest("U01.F01.T02");
  ::ReadRequestRefresh();
}