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APPENDIX A
What is the difference between Modbus and DNP3?
Modbus is an industrial protocol that has been used for many years. There are two
(2) variations of the Modbus protocol: ASCII and RTU
DNP3 is a newer protocol developed specifically for the utility industry. DNP3 can
be configured so that if an event occurs, the charger will send a message to the computer
system of any changes. This is called unsolicited messaging. DNP3 with unsolicited
messaging enabled detects the alarm and notifies the computer system immediately instead of
waiting for the computer system to poll for the status of the alarm.
Both protocols allow the computer system to query the charger for the current status.
What level of DNP3 does the AT Communications support?
The AT Communications Module supports DNP3 Level 2 with some advanced
features. Refer to the AT Communications Module operation manual (JA0102-04) for the
implementation of DNP3.
Can I communicate over the telephone?
Yes. A modem can be used to connect the AT Communications Module to an analog
phone line. The modem is should be set to auto-answer. The computer system will also need
a modem. The computer system will dial out to the AT Series charger. The modem
connected at the charger will answer the call and start communicating. Refer to the special
User Instructions (JA5070-00) for analog modem connection details.
Can I communicate to an AT Series Charger via a fiber optic connection?
Yes. An optional fiber optic to serial converter is available. This option, when
ordered, will be installed in the charger at the factory and will allow direct connection of
fiber connections compatible with standard "B&B" and "Dymec" type converters. Ethernet
connections over fiber optics wire are not supported at this time.
Can I connect the AT Series charger to an Ethernet network?
Yes. This connection requires the AT Series Communications module Ethernet
option (p/n EJ5037-2#).
What specific types of DNP3 over Ethernet are supported?
The AT Communications Module, when combined with the Ethernet option will
support DNP/TCP.
What specific types of Modbus over Ethernet are supported?
The AT Communications Module, when combined with Ethernet option will support
Modbus TCP\IP.
What types of Ethernet media are supported?
The AT Communications Module, when combined with the Ethernet option have a
10/100 Base-T port (supports 10 or 100 Mbps over copper). An Ethernet over Fiber option is
also available.
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