USB & RS232 Communication
Physical Layer
EPOS4 Communication Guide
2-20 CCMC | 2019-11 | rel8759
2.3 Physical Layer
2.3.1 USB
ELECTRICAL STANDARD
The EPOS4’s USB interface follows the «Universal Serial Bus Specification Revision 2.0». You may wish to
download the file from the Internet (for URL “Sources for additional Information” on page 1-5), full details
are described in chapter “7.3 Physical Layer”.
2.3.2 RS232
ELECTRICAL STANDARD
The EPOS4’s communication protocol uses the RS232 standard to transmit data over a 3-wire cable (sig-
nals TxD, RxD, and GND).
The RS232 standard can only be used for point-to-point communication between a master and a single
EPOS4 slave. It uses negative, bipolar logic with a negative voltage signal representing a logic “1”, and pos-
itive voltage representing a logic “0”. Voltages of -3…-25 V with respect to signal ground (GND) are consid-
ered logic “1”, whereas voltages of +3…25 V are considered logic “0”.
MEDIUM
For the physical connection, a 3-wire cable will be required. We recommend to install a shielded and twisted
pair cable in order to achieve good performance, even in an electrically noisy environment. Depending on
the bit rate used, the cable length can range from 3…15 meters. However, we do not recommend to use
RS232 cables longer than 5 meters.
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