L9780 datasheet(29/56 Pages) STMICROELECTRONICS

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L9780

Diagnostic

5.4.3

Heater open circuit

The device is able to distinguish between heater FET short to ground and open circuit

conditions. Once the heater open circuit test is invoked, the following actions are taken:

Turn off HD sink current generator;

Turn on HD source current generator;

If HD voltage value > open circuit threshold (specified in Table 13) a possible heater

open circuit is detected and immediately validated.

Actions

Once the heater open circuit fault is validated the following actions are taken:

Set the OCH bit in SPI output register;

Clear the STGH bit in SPI output register.

These actions remain valid until cleared by the user.

5.5

SPI diagnostic

Once a fault condition is reported in the SPI output register but the fault condition is

removed from the device, the user is able to clear the register and restore the normal

operative condition. This is possible using the CLEARFLT bit in the SPI input register. The

effect of this bit is to clear all the latched fault conditions and re enable every previously

disabled output; on HD pin sink and source currents are restored to their default condition.

The bit is then internally cleared when the clear operation is completed.

5.5.1

SPI data fault

The device continuously monitors the data input on SPI register. Bits 14 and 15 (CB0, CB1)

are the data confirmation bits and if one of their values is different from the expected

(CB0=0, CB1=1) an SPI data fault is detected and immediately validated.

Actions

Once an SPI data fault is validated the following actions are taken:

Ignore the corrupted message;

Assert SPIF1 and de assert SPIF2 bits in the output register; these bits are latched until

cleared by CLEARFLT;

Set REG bit to ‘0’.

L9780 Datenblatt(PDF) 29 Page - STMicroelectronics