392 JVL A/S - User Manual - Integrated Servo Motors MAC050 - 4500
6.9 Bus serial communication
6.9.1 Important information concerning RS-232.
Be sure to read this before trying to use RS-232 with any of the JVL modules or motors.
Also if you do not plan to use multidrop.
The widely used RS-232 connection is a point-to-point solution, where two systems are
connected by at least three wires: A common Grounds and two data wires, where data
is transmitted serially from TxD (Transmit Data) pin on the sender to a RxD (Receive Da
-
ta) pin on the receiver. In addition to this, sometimes hardware handshake signals are
used.
The baud-rate and address factory setting are set to 19200 baud and comport 1. The unit
can be set up via the MacTalk program. The motor shall be terminated, the MAC-B1, B2
and B4 expansion modul contain this feature. Opto isolation is recommended, and al
-
ways use screen cable. The interface cable should not exceed more than10 meters. Make
sure that GND is also connected.
The special RS-232 multidrop solution used with the products covered by this manual al-
lows more than two systems to be connected using the same wires.
With standard RS-232 the TxD pin in each end drives the signal to both high and low volt-
age levels, and it is an error to connect two or more TxD lines together since they would
conflict and generate invalid signal levels.
With the JVL multidrop RS-232 solution, the TxD line is only pulled to an active high
through a diode on the modules, and the line has a passive pull-down resitor that connect
the line to a negative supply voltage. This allows more than one module to drive the line,
but only one module can communicate data at a time.
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