The „IBIS-Transceiver“ is a compact module providing a TTL compatible interface for a low speed UART. The IBIS bus standard is being used in cars, trams and trains. A typical application is the use as a serial bus for non savety relevant interfacing to passenger ticket terminals or to passenger information displays. The module can be used as a „IBIS-Master“ or as a „IBIS-Slave“ node. It depends on the configuration setting.
On the low voltage logic side – 5VDC TTL, the connection is being made to an industry standard UART interface, Rx and Tx with no support for HW handshake. It is not required for this kind of low speed application. The „IBIS-Master“ uses a standardized protocol in order contact the IBS slave nodes. All requests are being initiated from the master only. The IBIS transmission and reception circuitry is being isolated from the low voltage TTL side through opto-couplers – 1KVeff. The supply for the IBIS power driver, receiver is being taken from the vehicle internal 24VDC +- 30%.
The challenge for this very simple looking circuitry has been the large signal voltage swing of 24V, the sinkable and sourceable current (700mA) for the IBIS master, the overal length of the line and the number of slave nodes along the line. Additionally no line termination can be used. This requires well controlled rise and fall times during signal transition.