Connect Tech CTIM-00044 user manual Bus Contention on Differential Multi-drop Networks

Connect Tech Blue Heat/Net Sync User Manual

Bus Contention on Differential Multi-drop Networks:

Bus contention occurs when two or more devices enabled on a bus attempt to run the bus to opposite logic values. From the diagram above, we can see that there are multiple differential transmitters (TXD) on the bus. To avoid the bus contention problem, the differential transmitter features a tri-state, or high impedance mode controlled by an input pin (enable). Software and hardware in the Blue Heat/Net Sync and the differential devices will always place its transmitter into the high impedance mode when not transmitting. This feature is managed by the Blue Heat/Net Sync and is fully transparent to your application.

For example, in a multi-drop network, the differential transmitter is enabled prior to the master initiating transmission. When transmission is complete, the transmitter is placed in high impedance mode. Each slave will receive that transmission from the master. (A protocol must be in place to address, or select, the desired slave device, but that discussion is beyond the intentions of this tutorial, and is entirely application dependent). When the slave device has received the data, it will respond by enabling its transmitter and transmitting data onto the bus, then placing its transmitter into high impedance mode, just as the master did.

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