• The 3964R protocol (also referred to as DUST) provides the link layer functionalities, so it is not a fully functional protocol in a proper sense. It supports transparent transmission of data blocks on point-to-point connections, operating in half-duplex mode.

    The physical layer operates in asynchronous standard mode (1 start bit, 8 data bits, 1 parity and 1 stop bit) using the ISO 7 bit character code for control commands (such as DLE, STX, ETX). 

    There are two variants::

    • 3964
      only parity is used to ensure data integrity
    • 3964R
      in addition, horizontal parity is used to ensure data integrity

    The protocol has been very popular in process automation, in particular for data exchange between devices with Simatic-SPS. 3964R is also used as link layer for a Sinaut 8FW variant.

7 Application Layer n/a
6 Presentation Layer n/a
5 Session Layer n/a
4 Transport Layer n/a
3 Network Layer n/a
2 Link Layer 3964
1 Physical Layer RS232 (V.24), RS485
Applicable Products
  • ipConv

    Universal protocol converter for highest degree of flexibility