Electrolux EMP-800 Service Manual download pdf (Page 30)

Technical Manual EMP 8x0.00/04/13 v5 wh Münzprüfer Dietmar Trenner GmbH, Germany

Version 1.51

Page 30/42 subject to technical modification EMP8x0.00/04/13 v5

3.3 Multi Drop Bus (MDB)

The coin selector can be set up to communicate with the machine controller using

the MDB protocol. wheasy 3 can be used to program this setting. Select

“Settings”, then “Operating Mode“. Choose MDB. Also be sure that the “Multi

Drop Bus” check box is checked under “Configuration,” “B-Values” and then select

the “Mode” tab.

! The EMP 800 v5 has an implementation of the MDB protocol

according to I.C.P. (MDB European Version). The still free available

address 15 h was chosen in order to avoid conflicts with other MDB

devices. The command set and the bus timing correspond to I.C.P.

standard. Additionally a MDB adapter is available if the hardware

specification of the interface is also requested.

3.3.1 Protocol Specifications

• Data format: 1 start bit

8 data bits

1 mode bit

1 stop bit

• Mode bit: VMC to EMP

The mode bit distinguishes ADDRESS bytes and DATA bytes. ADDRESS bytes

are read by all peripheral devices and DATA bytes are only read by active

peripheral devices. An active peripheral device is defined as a device that has

successfully established a contact with the master (VMC).

The mode bit is set (logically 1) in order to mark an ADDRESS byte. When the

mode bit is not set (logically 0) it marks a data byte.

• Mode bit: EMP to VMC

The mode bit is set with the last byte when the slave (EMP) is transmitting data to

the master (VMC). Consequently, the slave (EMP) always sets the mode bit

together with the check sum or with ACK.

• Check sum

The last byte of every data transfer from the VMC to the EMP is always the check

sum.

3.3.2 Conventions

Using the Multi drop Bus all commands and answers must be answered within 5

milliseconds or acknowledged respectively!

The coin selector answers every command and every polling within 5 milliseconds.

If the coin selector is busy and therefore can not answer within the 5 milliseconds

the selectors looses the command. The VMC (Vending Machine Controller) must

handle this as a NACK (FFh).

All answers from the coin selector to a poll command must be acknowledged

through the VMC within 5 milliseconds with ACK (00h). If no acknowledgement has

been received within 5 milliseconds the coin selector handles this as a NACK and

transmits the same answer on the next poll command again.

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Electrolux EMP-800 Service Manual Page 30

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