L9963E datasheet(36/184 Pages) STMICROELECTRONICS

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4.2.4.4

Special frames

Table 30. SPI protocol special frames

Frame Type

Frame Code

Frame Issued

Default

0x0000000016

After a wake up event

Not Expected

Frame

0xC1FCFFFC6C

In a Burst access, in case the MCU clocks a number of answer frames higher than

the expected

Timeout Frame

0xC1FCFFFC87 In case no answer is received after the timeout TSPI_ERR.

Busy Frame

0xC1FCFFFCDE

In case the MCU sends a frame while the Master device is still transmitting or waiting

for an answer (TSPI_ERR not expired)

CRC Error Frame

0xC1FCFFFD08

In case a unit configured in SPI mode (SPIEN = 1) receives a corrupted frame. When

a unit is configured in isolated SPI mode (SPIEN = 0), no answer will be issued upong

CRC error detection.

4.2.4.5

Global Status Word (GSW)

The global status word is made of 2 bits. The MSB (bit 25) is dedicated to the the internal fault detection (all

failures except the FAULTH detection), while the LSB (bit 24) implements the Rolling counter:

Table 31. GSW code description

GSW

Description

0X(1) L9963E hasn’t detected any internal failure (but could be propagating a failure from an upper device in the stack)

1X(1) L9963E has detected an internal failure (and could be also propagating a failure from an upper device in the stack)

1. 'X' = don’t care.

The GSW can be exploited by the MCU fault handling routine to understand which device of the daisy chain has

self-detected a failure.

4.2.4.6

CRC calculation

Each frame is equipped with a 6-bit CRC code in order to guarantee information integrity. In case a unit receives a

corrupted frame, it will be discarded.

Table 32. CRC calculation information

CRC

Length

6 bit

Polynomial

X6 + X4 + X3 +1

Seed

0b111000

4.3

FAULT line

The FAULTL/FAULTH pin pair provides an isolated communication interface exploiting optical-isolators to

implement uni-directional transmission of the failure signal from the highest L9963E in the stack down to the

μC.

The FAULT line main purpose is to interrupt the MCU activity in case one of the daisy-chained L9963E detects

a failure. Recommended interrupt handling routine should implement a strategy to detect which of the several

L9963E has self-detected a failure. This can be easily done by sending a communication frame to each L9963E,

reading back the corresponding fault bit of the Global Status Word (GSW).

Any failure is propagated/generated by an upper device via its FAULTL pin. It is then sensed by a lower device on

its FAULTH pin.

For the circuit and the BOM, refer to Section 6.7 FAULT line circuit.

L9963E

FAULT line

DS13636 - Rev 12

page 36/184

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