Technical Manual EMP 500 v7 /CLB WH Münzprüfer Dietmar Trenner GmbH, Germany
version 2.7
page 42/62
subject to technical modification
EMP 500 v7 /CLB
4.3.
Multi Drop Bus (MDB)
The coin selector can be set up to communicate with the machine
controller using the MDB protocol. wheasy 5 can be used to program this
setting. Select “Configuration” –
“Interfaces”. Set the operating mode to
MDB/ccTalk.
The EMP 500 v7 /CLB has an implementation of the MDB
protocol according to I.C.P. (MDB European Version). The still
free available address 0Fh (15Dez) 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 (MDB 100) is available if the hardware
specification of the interface is also requested.
After each “Reset” the coin selector will be set automatically
to either MDB or ccTalk communication depending on the first
command received from the host. The first command may only
be sent after the “start up period” of 20 milliseconds.
4.3.1.
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.
4.3.2.
Conventions
Using the Multi drop Bus all commands and answers must be answered
within a given period or acknowledged respectively!
The coin selector answers every command and every polling within 5
milliseconds. If the coin selector is busy and therefore cannot answer
within the 5 milliseconds the selector no longer retains the command. The
VMC (Vending Machine Controller) must handle this as a NACK (FFh). All