Multi-drop bus to RS-232 or USB PC interface ( MDB-RS232 )

The vending machine standard NAMA Multi-Drop Bus (MDB) may now be interfaced to a PC using the MDB-RS232. The MDB-RS232 allows Coin Acceptance, Change Dispensing, smart card reader, magnetic swipe, credit card reader and bill validation all controlled by the PC.Conforms to all NAMA MDB specification and is compatible with any MDB compliant vending device. Hardware interface comes with cables,user's guide and user's protocal.

This Interface Unit (IU) is designed to convert the MDB Bill Acceptor (BA) and MDB Coin Changer (CC) protocol to RS-232 serial protocol. The IU functions as a slave to a master control system. The master may be any control system that supports RS-232 serial communication, for example a PC.

DESCRIPTION：
This Interface Unit (IU) is designed to convert the MDB Bill Acceptor (BA) and MDB Coin Changer (CC) protocol to RS-232 serial protocol. The IU functions as a slave to a master control system. The master may be any control system that supports RS-232 serial communication, for example a PC.

OPERATION:
The master and slave communication is based on master requests and slave replies. The master sends a status request (or command) to the IU and IU answers by sending its current status. The IU’s typical response to the Master’s request (polling) consists of a header and data bytes. If there is no BA or CC activity, the status is one byte, the header only. When the IU receives data from the BA or CC, it sends a header followed by data bytes in the response to master’s status request. The master must always poll (query) the IU. If the IU does not receive a query from the master in the predefined time slot or IU does not recognize master messages 10 times in row, it will inhibit the BA and CC acceptance. At power up, acceptance of the BA and CC is inhibited.

SPECIFICATION:
Communication format:

Baud rate	Start bit	Data bits	Parity	Stop bit
9600 BPS	1	8	NO	1

Timing Specification:

Hardware Specification.