User Manual

TMCM-1311 V1.2 Hardware Manual (Rev. 1.12 / 2013-JUL-05) 16
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3.4.2 CAN
For remote control and communication with a host system the TMCM-1311 provides a CAN bus interface.
To select a modules’ address, the TMCM-1311 is equipped with dip switches with digits from 1 to 4.
Anyhow, the switches use the binary digit system. Thus, node addresses from 1 to 15 can be set.
THERE ARE TWO POSSIBILITIES FOR THE ADDRESS SETTING
- All DIP switches off: RS485 address is taken from the on-board non-volatile memory (EEPROM).
Factory default value for the module address is 1.
- At least one DIP switch on: the 4 DIP switches define the CAN address. The address is specified as
binary 4bit value – DIP switches 1… 4 specify bit 1… 4 of the address
Figure 3.6 Dip switch for address selection
Note
- Per default, all dip switches are off and the module address taken from the EEPROM is 1. Per default,
the host address is 2.
- Do not use equal addresses for the host and the TMCM-1311!
For proper operation the following items should be taken into account when setting up a CAN network:
1. BUS STRUCTURE
The network topology should follow a bus structure as closely as possible. That is, the
connection between each node and the bus itself should be as short as possible. Basically, it
should be short compared to the length of the bus.
c:>
node
1
node
n
- 1
node
n
Host
Slave Slave Slave
CAN
termination
resistor
(120 Ohm)
termination
resistor
(120 Ohm)
}
keep distance as
short as possible
Figure 3.7 CAN bus structure
2. BUS TERMINATION
Especially for longer busses and/or multiple nodes connected to the bus and/or high
communication speeds, the bus should be properly terminated at both ends. The TMCM-1311
does not integrate any termination resistor. Therefore, 120 Ω termination resistors at both ends
of the bus have to be added externally.
3. NUMBER OF NODES
The bus transceiver used on the TMCM-1311 units (TJA1050T) supports at least 110 nodes under
optimum conditions. In practice, the achievable number of nodes per CAN bus highly depends
on the bus length (longer bus -> less nodes) and on the communication speed (higher speed ->
less nodes).