Multi-Drop Bus / Internal Communication Protocol

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Multi-Drop Bus / Internal Communication Protocol (MDB/ICP) is the latest, US-European iteration of a

networking protocol used within the vending machine industry, currently published by the American National Automatic Merchandising Association and supported by the European Vending Association and the European Vending Machine Manufacturers Association. It is based on earlier protocols (also known as MDB in the US) dating back to at least the early 1990s.[1][2]

Mechanism

The multidrop bus used by

microcontrollers
.

The physical connection is realized as a serial bus with a fixed data rate of 9600 baud. There are just 2 communications signals plus the essential common-ground reference signal. The TX signal goes from the MASTER to every SLAVE device. The RX signal goes from every SLAVE device to the MASTER device. Both signals have pull-ups. The bus is driven at every transmitter by an open collector transistor driver, and isolated at each receiver with an opto-isolator - though cable harnesses carrying the communication signals may also carry 24-volt power and ground signals to devices, meaning the devices may not be isolated from each other as they share the same power bus. Some devices, however, may have alternate power supplies, especially devices with motors and high current needs such as vintage bill acceptors or currency detector devices.

History

MDB originated as a proprietary bus used by CoinCo for their coin-acceptors in the late 1980s and was deployed in high volume in vending machines for

Smartcard
based) to be connected to existing vending machines.

Bus addressing is based on the device type only, which allows for a very simple protocol stack, as no initial enumeration needs to be performed.

Timeline

  • August, 2019: Version 4.3 released (seventh MDB release)[4]
  • February, 2011: Version 4.2 released (sixth MDB/ICP release)[1]
  • July, 2010: Version 4.1 (fifth MDB/ICP release)
  • April, 2009: Version 4.0 (fourth MDB/ICP release)
  • March, 2003: Version 3.0 (third MDB/ICP release)[5]
  • October, 2002: Version 2.0 (second MDB/ICP release)
  • October, 1998: Version 1.0 (first MDB/ICP release)
  • 1994: Revised EVMMA document.
  • August, 1994: Revised NAMA document.
  • 1994: Original EVMMA document.
  • October, 1993: Original NAMA document.
  • Earlier US versions were known as MDB rather than MDB/ICP. Prior to this, it was allegedly a proprietary protocol developed by CoinCo.

See also

External links

References

  1. ^ a b "Multi-Drop Bus / Internal Communication Protocol - MDB / ICP - Version 4.2" (PDF).
  2. ^ "Overview of Vending Machine Interfaces" (PDF). European Vending Association. 2012.
  3. ^ "MDB Specification Version 4.2" (PDF). NAMA. Archived from the original (PDF) on 2015-06-27. Retrieved 2018-10-11.
  4. ^ "MDB v4.3" (PDF).
  5. ^ "Multi-Drop Bus / Internal Communication Protocol - MDB / ICP - Version 3.0" (PDF). Archived from the original (PDF) on 2018-05-17.
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