The client’s field length configuration must match the setting of the IEC 60870-5-104 instance. Sometimes it may not be possible to configure these fields in the client. In such a case, the IEC 60870-5-104 settings must be forced to adjust to match the client.
Regarding Device address and “Common address of ASDU”, a decision whether to use 1 or 2 octets addressing must be taken. The default setting of Link address length and ASDU address length, 1 octet, means that no higher addresses than 255 can be used.
The configuration of the field length and the actual setting value for the field are not cross-checked. If, for example, IOA length is set to "1" octet, all configured data points with higher object addresses than 255 get their higher address byte masked out. For example, IOA address 4500 (Hex 1194) occurs as 148 (Hex 94). If another data point with address 148 has been created, these objects overlap one another.