The Schneider/Modicon "Modbus II" Protocol


Thread Starter

Lynn Linse

Whenever you connect with ModSoft to a com port, you have a number of protocol options including "Modbus II".

A while ago I was verbally told by someone at Schneider that this was a derivative of Modbus-Plus designed to be tunneled across a serial link. It looked like Modbus/RTU with RTU CRC, but instead of the 1-byte Slave address of RTU it had the 5-byte path of ModbusPlus. This allowed the MB+ message to bridge thru serial links without loss of the path.

I'm curious if anyone out there has ever seen a formal definition of this "Modbus II" & can confirm this?


Lynn August Linse, Senior Product Application Engineer
15353 Barranca Parkway, Lantronix Inc, Irvine CA 92618
[email protected]
Tel: (949)300-6337 Fax: (949)453-7132
Modbus II is a MAP3.0 compatible protocol. Media is coax cable and speed could be up to 5/10M. Since it's some what expensive, few users use it, so. It's not present in current product line. The core net work for time being for Schneider is Web enabled TCP/IP Ethernet, up to 100MB.

Rob Entzinger

Modbus II is base on Manufacturing Automation Protocol (MAP) and runs on a coax cable. I think it was base on the MC68824 Token bus controller. It operates at 5Mbps, supporting upto 64 stations (addresses 1-255)which function as peer members of a token-passing logical ring.

Refer to manual GM-MBII-04A revision AX03.

Hope this helps
Rob E.
Lynn --
The Modbus II protocol is a mini-MAP protocol, using 3 of the 7 layers of the MAP protocol. The message encoding was MMFS, and the link layer was of token bus design. It predates Modbus+.

The formal definition is in the MODICON Modbus II Network Subroutine Library User's Guide (GM-MBII-04A).

Rich Baker
Engineering Manager
(including the Modbus II project in the late 1980s)
Schneider Automation

Phillip O'Meley

Modbus II was pre IEE 802.4 days. In my market place (Oz) it wasn't pursued when MB+ arrived in the early 90's
Phill O'Meley