LNBH21

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DiSEqCTM IMPLEMENTATION

The LNBH21 helps the system designer to implement the bi-directional (2.0) DiSEqC protocol by allowing

an easy PWK modulation/demodulation of the 22KHz carrier. The PWK data are exchanged between the

LNBH21 and the main µP using logic levels that are compatible with both 3.3 and 5V microcontrollers.

This data exchange is made through two dedicated pins, DSQIN and DSQOUT, in order to maintain the

timing relationships between the PWK data and the PWK modulation as accurate as possible. These two

pins should be directly connected to two I/O pins of the µP, thus leaving to the resident firmware the task

of encoding and decoding the PWK data in accordance to the DiSEqC protocol. Full compliance of the

system to the specification is thus not implied by the bare use of the LNBH21. The system designer should

also take in consideration the bus hardware requirements; that can be simply accomplished by the R-L

4. To avoid any losses due to the R-L impedance during the tone transmission, the LNBH21 has

enabled by setting the TTX SR bit HIGH only during the tone transmission (see DiSEqC 2.O operation

description on page 2).

pin can be directly connected to the LNB supply port of the Tuner (see DiSeqC 1.x application circuit on

pag.4). There is also no need of Tone Decoding, thus DETIN and DSQOUT pins can be left unconnected