L9663 datasheet(84/104 Pages) STMICROELECTRONICS

84 / 104 page

Communication interface

L9663

84/104

DocID028693 Rev 1

CRC generation is based on the same calculation scheme used for PSI5 sensor data

(generator polynomial g(x)=1+x+x3, initialization value "111") with MSB passed first.

CRC error is generated in case of mismatch (last two bits are inverted)

Figure 27. Operation on internal register (with upstream data buffer)

Figure 28. Init data reading

Sensor data Reading:

Timeslot coding: Timeslot1=001, …, timeslot6=110

SID and Gbit are supported only for 10 - 16 bit and enabled by 1 single configuration bit =

GCR1(2)

Two kinds of transfer are possible:

No SID, payload ≤ 20 bit; SID and GBIT, payload ≤ 16 bit: one transfer needed

No SID, payload > 20 bit: two transfers are needed.

In case 1) the L/H bit must be L (0); if a H (1) is requested on a sensor which fits in 1 SPI

frame a SPIE is generated and a CRC error is generated.

In case 2) the device expects a sequence H - L on the L/H bit to transmit first the MSB part

of the data and then the LSB. If the sequence is not the one above, a SPI error is generated

and a CRC error is generated.

To guarantee a safe communication with two SPI transfers:



if CRC is the one from the sensor (GCR1(1)=0) , CRC is the same on both transfers

and it's the one from the sensor;



if CRC is calculated on SPI (GCR1(1)=1), CRC is calculated over bits 26:3 in each

frame.

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