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STM8SPLNB1

DiSEqC™ protocol basics

Appendix A

DiSEqC™ protocol basics

For better understanding the document is here small overview of DiSEqC™ protocol (Digital

Satellite Equipment Control).

A.1

Physical layer

The DiSEqC™ message is transferred between master and slave(s) through existing

coaxial cable which delivers also the HF signal. The slave device(s) can be also powered

through the same coaxial cable from master.

A.1.1

DC voltage on coaxial cable

Powering of the slave devices is performed by applying DC voltage on HF signal. The

voltage level should be from 13 V to 18 V. Slave device uses this voltage for powering itself

after some voltage regulator (e.g. +5 V regulator).

The voltage level also signalizes different DiSEqC™ state. There exists 2 states:



13 V voltage level



18 V voltage level

Those states are used in DiSEqC™ protocol signalization - horizontal or vertical polarization

selection.

A.1.2

22 kHz signal on coaxial cable

To the signal on coaxial cable - HF signal and DC voltage - can be modulated 22 kHz signal.

Presence of 22 kHz signal signalizes different state and is used in DiSEqC™ protocol

signalization. Amplitude of 22 kHz signal is around 0.5 Vpp (peak to peak).

22 kHz tone presence selects High frequency band and no tone selects Low frequency

band.

Satellite selection (satellite A or B) is made also according 22 kHz tone. If 22 kHz tone is

transmitted continuously then satellite A is selected. If 22 kHz tone is transmitted in burst

sequence then satellite B is selected (duration of this selection is 12.5 ms).

Figure 19. Timing diagram for Tone Burst control signal

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