L9963T datasheet(36/45 Pages) STMICROELECTRONICS

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4.4

Managing ISOFREQ and TXAMP pin for communicating with L9963T

Both L9963T and L9963 feature the capability of communicating with different bit rate and amplitude settings. In

order to avoid losing frames upon bit rate/amplitude switching, the following indications must be followed:

•

To switch both devices from low to high frequency:

Set ISOFREQ = 1

Send the command programming L9963 iso_freq_sel bit to 0b11. L9963T will send the frame in low

frequency, but L9963 will answer back in high frequency. L9963T is already configured to receive

answers in high frequency and no data will be lost.

•

To switch both devices from high to low frequency:

Set ISOFREQ = 0

Send the command programming L9963 iso_freq_sel bit to 0b00. L9963T will send the frame in high

frequency, but L9963 will answer back in low frequency. L9963T is already configured to receive the

answers in low frequency and no data will be lost.

Switching the amplitude alters the communication SNR. In principle, L9963 and L9963T could correctly

communicate even if their amplitude settings are different. However, it is recommended to configure both devices

with the same amplitude in order to reach a robust SNR.

•

To switch both devices from low to high amplitude:

Set TXAMP = 1

Send the command programming L9963 out_res_tx_iso bit to 0b11. L9963T will send the frame with

low amplitude, but L9963 will answer back with high amplitude. L9963T is now configured to send

frames with high amplitude.

•

To switch both devices from high to low amplitude:

Set TXAMP = 0

Send the command programming L9963 out_res_tx_iso bit to 0b00. L9963T will send the frame with

high amplitude, but L9963 will answer back with low amplitude. L9963T is now configured to send

frames with low amplitude.

L9963T

Managing ISOFREQ and TXAMP pin for communicating with L9963T

DS13590 - Rev 4

page 36/45

L9963T Scheda tecnica(PDF) 36 Page - STMicroelectronics