Payment Technology
MDB 4.3: A bus protocol for cashless vending payments
Term from the vending glossary
This article was created with AI assistance and checked automatically. A human review before publication is not documented. MDB/ICP (Multi-Drop Bus / Internal Communication Protocol) is a serial interface standard for communication between a vending machine controller and peripheral devices. Version 4.3, dated July 2019, updates the cashless-device section of the protocol.
What does MDB 4.3 do?
MDB defines how an electronically controlled vending machine communicates with peripherals such as payment devices. The vending machine controller (VMC) acts as the master; peripherals act as slaves. The specification sets out communication formats, bus timing, hardware requirements and device-specific protocols. Its stated baud rate is 9600, with a maximum response time of 5.0 ms for a valid communication.
What changed in version 4.3?
The July 2019 release is the seventh version of the international MDB/ICP specification. Its revisions are in Section 7, covering cashless devices. The changes include reporting the dispensed item number, “Remote Vend,” basket transactions with partial refunds, coupon handling and support for card information in selection-first transactions. These are protocol capabilities; a particular machine or payment terminal must implement the relevant functions for an operator to use them.
What should operators check?
Before buying a cashless terminal or commissioning a machine, ask the supplier which MDB version and cashless functions the specific controller and terminal support. Confirm compatibility and any required configuration in writing. MDB 4.3 is an interface and protocol specification, not a specification for the complete vending system, so the version number alone does not establish that every feature is available. The MDB/ICP Version 4.3 specification is the primary reference for technical requirements.