Rockwell Automation 6001-F2E AB STANDARD DRIVER SFTW - Manual (Page 19)

Writing Your Own Application Program
Chapter 4
4-6
Preventing Reply Messages from Being Lost
To prevent reply messages from being lost, we provide a Get_tns()
function. Use the following format:
x = Get_tns()
The Get_tns() function returns an unsigned integer value. Place this value
in the two-byte TNS field of your DH-485 message prior to calling the
Send_StdDrv() function. See page B-5 for more information on
Get_tns().
The Get_ErrMsg() function call supplies a message string for errors in
data transmission. If an error occurs, call Get_ErrMsg() with the error
code to get a message indicating the problem. Use the following format
and parameters:
Format for Get_ErrMsg()
The Get_ErrMsg() function call is shown below:
Get_ErrMsg(err, ret_msg);
Parameters for Get_ErrMsg()
Table 4.E explains the parameters:
Table 4.E
Get_ErrMsg() Parameters
Parameter Type Description
err unsigned int is a copy of the error value returned in io_stat[0].
ret_msg char is a pointer to a character buffer at least 80 characters long. It contains
the error message string that corresponds to the code in the err
parameter. The error message is returned in this buffer.
Table 4.F explains how to read io_stat[0] to get the STS and EXT STS
bytes.
Using Get_ErrMsg()