Since DiSEqC can be implemented as an unidirectional (DiSEqC 1.X) as well as bidirectional system (DiSEqC 2.X), there are different versions of bus modems, with a major difference between bus powering master device modems and remote powered slave modems.

In a unidirectional DiSEqC system the existing satellite receiver hardware used for applying the 22kHz tone can be used for modulating the DiSEqC data.

In the Slave a single transistor amplifier lifts the burst packets amplitude from 300mVpp up to TTL level for the slave microcontroller.

For the bi-directional data communication somewhat more hardware is necessary. The power supply of DiSEqC 2.X receivers contains a RLC combination, which determines power pack impedance to 15 Ω (at 22kHz). The transmitters in master and slave are realised as pulsed current sinks, which pulls 22kHz pulses with about 45mA from the remote power rail. The voltage drop occurring over the RLC impedance modulates the bus voltage with approximately 0.5Vpp.

The DiSEqC receiver in the master is identical to the one in the DiSEqC slave.

Pagina 15 / 29