L9963T datasheet(13/45 Pages) STMICROELECTRONICS

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Figure 7. BNE/CPOL pin structure

3.2.1.6

TXEN/CPHA

TXEN_CPHA is a digital input pin whose configuration depends on the value of NSLAVE latched during

Trimming & Config Latch:

•

When NSLAVE = 0 (Slave Configuration) the pin works as transmitter enable input TXEN:

–

MCU should release TXEN (or pull it up actively) prior to NCS assertion in order to enable the

transmission of the data from SDI input buffer to the TX queue (and then to the isolated SPI interface).

◦

In case the communication protocol does not feature any burst read capability, each command

sent by the master unit will generate a single answer from the addressed slave unit. Hence TXEN

pin can be connected to VDD in order to keep the transmitter permanently enabled.

–

In case of burst read operations, where user SW has to empty the RX queue without transmitting any

frame on the isolated SPI, the TXEN input must be pulled down before beginning the burst read.

◦

Even if data on the SDI line is discarded while TXEN = 0, it is highly recommended that MCU

sends dummy frames (or intentionally corrupted frames) on the SDI line during the burst read.

In the event of TXEN stuck high, such frames will generate errors according to the implemented

communication protocol.

–

To avoid chopping frames currently being transmitted, the TXEN pin is latched upon NCS assertion.

Therefore, it must be stable at least TTXEN_DEGLITCH + TTXEN_SETUP before NCS assertion. Moreover,

TXEN must be kept stable TTXEN_HOLD after NCS assertion in order to fulfil hold time constraints.

L9963T

Pin configuration

DS13590 - Rev 4

page 13/45

L9963T Datasheet(PDF) 13 Page - STMicroelectronics