Computer Peripheral for interfacing
MDB protocol devices with a personal computer
The MDB2PC™ is a Computer Peripheral for interfacing vending machine
protocol used by various devices including: Dollar Bill Validators, Coin
Acceptors, Coin Dispensers, Smart Cards, Foreign Currency etc.This describes the Interface Protocol for the MDB2PC™ Hardware
circuit. The MDB2PC™
is a microprocessor controlled hardware interface with embedded firmware that
converts the MDB protocol to an RS232 protocol.
What is MDB and why do I
need the MDB2PC™?
MDB stands for "Multi-Drop Bus" and is a protocol
developed by vending machine industry. The "Multi-drop Bus" (MDB) protocol is
not compatible with the standard RS-232 PC protocol and therefore a hardware and
software interface is necessary. The MDB2PC™
is a microprocessor controlled hardware interface with
embedded firmware that converts the MDB protocol to an RS232 protocol and also
performs the necessary voltage conversion. The MDB2PC™
also relieves the Polling requirements thereby allowing the same PC to perform
The MDB2PC™ is
necessary to interface the industry standard MDB Vending machine protocol to a
standard PC because:
- The MDB uses 11 Bits and a nine (9) bit byte.
- The polling requirements for the various MDB devices are excessive (20-200
- A non-dedicated PC can not meet the polling requirements.
- The MDB2PC™ takes care of the polling requirements and generates
an interrupt on the serial port of the PC.
- This methods allows the PC to perform normal operations and respond to
interrupt driven comm events in the UART buffer.
- All data from an MDB device is available to the PC.
- Additionally, all commands can be sent to the MDB device from the PC (ie.
dispense, write to smart card etc...)
The MDB2PC™ interfaces any MDB vending device (6-pin molex/5pin MTA)
to the PC via the serial port (DB-9).The MDB2PC™ protocol is compatible with standard RS-232
Up to eight (8) MDB compliant devices may be attached to a single MDB2PC™.
The programming interface is user-friendly and may be downloaded for free.
Sample source code
is available and may be freely distributed. We also offer a
Any MDB compliant device may be interfaced to a PC. This now makes it
possible to accept and dispense any coin types including foreign currency and
Euro Dollar (when available)
MDB compliant smart card readers can now be accessed.
24 to 35 Vdc
90 ma Typical
300 ma Maximum
Operating Temp 32°F to 158°F
0°C to 70°C
Storage Temp -22°F to 165°F
-30°C to 74°C
Relative Humidity 5% to 95% Non-condensing
< 1 lb
Length 4.0 inches Width 3.0 inches Height 1.1 inches
PWR 24-35V Pin 2 +24Vdc Nominal
Pin 4 Ground
MDB Pin 1 +24Vdc Nominal
Pin 2 Ground
Pin 3 N/C
Pin 4 MDB Receive Data
Pin 5 MDB Transmit Data
Pin 6 Common
RS-232 Pin 1 N/C
Pin 2 PC Transmit Data
Pin 3 PC Receive Data
Pin 4 DTR
Pin 5 Ground
Pin 6 N/C
Pin 7 N/C
Pin 8 CTS
Pin 9 N/C
D3 MDB Activity
D4 PC Activity
D5 Status 1
D6 Status 2
Jmp1 Mode Select 1
Jmp2 Mode Select 2
MTBF Actual TBD
Estimated 250,000 Hrs.