Instruction Manual

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:

able 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 buf

fer.

Table 4.F explains how to read io_stat[0] to get the STS and EXT STS

bytes.

Using Get_ErrMsg()