AN4124 datasheet(16/32 Pages) STMICROELECTRONICS

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FCCU settings

AN4124

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Doc ID 023294 Rev 2

Description

First the microcontroller is in DRUN mode, the “if” condition is asserted, by the tc0_INIT

procedure. The FCCU is configured in the tc0_INIT. Next the CF 20 is injected (in order to

generate an NMI, without RESET). When the injection fault is asserted (FCCU.CFF.R = 20),

the system asserts NMI. In NMI ISR the fault is cleared and the system enters RUN mode.

5.2.1

FCCU init

uint16_t tc0_INIT(void){

/* ----------------- CONFIG State --------------------- */

FCCU.CFG_TO.R = 0x7;/* Set Timer Out CCONFIG STATE to 8.192 ms */

FCCU_CONFIG_STATE();/* CONFIG state */

FCCU.CFG.B.SM = 1; /* EOUT protocol (dual-rail, time-switching) fast switching

mode*/

FCCU.CFG.B.PS = 1; /* fcc_eout[1] active low, fcc_eout[0] active low */

FCCU_CFG_FOM_Config(CFG_FOM0); /* CFG_FOM0 = Dual-Rail (default state)

[fccu_eout[1:0]= outputs] */

FCCU_CFG_FOP_Config(0); /* Fault Output Prescaler= Input clock frequency

(ipg_clk_safe clock) is divided by 2 x 1024 */

/* Set the Critical Fault reaction */

FCCU.CFS_CFG0.R = 0; /* No reset reaction */

/* ----------------- NORMAL State --------------------- */

FCCU_NORMAL_STATE();/* NORMAL state */

return(PASS);

}

5.3

Example 3: FCCU - Non-critical fault injection

In this example we show fault injection (with fake funtionality), in order to show an FCCU

reaction. The example is with FAULT_ISR assertion. The fault is checked and cleared in

FAULT_ISR subroutine by looking in the CFSx registers.

Example description

●

Put FCCU in CONFIG state: set registers.

●

Return to NORMAL state: by means of procedure or by allowing timer out to elapse.

●

Inject (fake) faults (NCF N. 12).

●

Verify that in RUN state (FAULT_ISR management), and that fault is detected

(FCCU_NCFS0 register).

●

Clear the FCCU_NCFS0 register (by suitable procedure).

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