26. Software Modem Device (SMD)

The SMD is a block for communication via a modem's Digital Isolation Barrier (DIB) with a complementary Line Side Device (LSD). Power and clock are supplied by the SMD and consumed by the LSD. The data flow is bidirectional. The data transfer is based on pulse width modulation for transmission from the SMD to the LSD, and for receiving from the LSD.

It has two bidirectional channels, a data and a control channel. The data channel is used to transfer digitized signal samples at a constant rate of 16 bits at 16 kHz, whereas the control channel is used to communicate with control regiters of the LSD at a maximum rate of 8 bits at 16 kHz.