JVL MAC050 User Manual page 278

5.9
The typical use scenario is that one PC or PLC is connected to two or more JVL modules
and each module has it's own unique address, so the PC/PLC can address one module at
a time and receive an answer on the shared line. It can then address the next module with
another address. For this to work, exactly one of the modules on the line must have the
passive pull-down resistor enabled. If there is only one module connected to the PC/
PLC, that module must have its pull-down resitor enabled.
In the JVL documentation, this system is called TXPD (for TX data resistor Pull-Down).
TXPD is enabled by setting DIP switches on the expansion modules, find the module in
section 4 of this user manual.
The baud-rate and the address factory setting are set to 19200 baud and address 1. Opto
isolation is recommended, and always use screen cable. The interface cable should not
exceed more than 10 meters. Make sure that GND is also connected.
5.9.2 Important information concerning RS-485
Please read this before using RS-485 serial-port. This note describes some important de-
tails of using this interface.
The most important difference to a standard RS-485 solution is that the MAC00-xx
modules drive the line transmit mode for up to one byte-time longer than required.
274 JVL Industri Elektronik A/S - User Manual - Integrated Servo Motors MAC050 - 800
Bus serial communication