Datasheet

SAM9G20
DS60001516A-page 776  2017 Microchip Technology Inc.
• The main code:
//user reset interrupt setting
// Configure AIC controller to handle System peripheral interrupts
AT91F_AIC_ConfigureIt (
AT91C_BASE_AIC, // AIC base address
AT91C_ID_SYS, // System peripheral ID
AT91C_AIC_PRIOR_HIGHEST, // Max priority
AT91C_AIC_SRCTYPE_INT_EDGE_TRIGGERED, // Level sensitive
sysc_handler );
// Enable SYSC interrupt in AIC
AT91F_AIC_EnableIt(AT91C_BASE_AIC, AT91C_ID_SYS);
*AT91C_RSTC_RMR = (0xA5<<24) | (0x4<<8) | AT91C_RSTC_URSTIEN;
• The C SYS handler:
extern void soft_user_reset(void);
void sysc_handler(void){
//check if interrupt comes from RSTC
if( (*AT91C_RSTC_RSR & AT91C_RSTC_URSTS ) == AT91C_RSTC_URSTS){
soft_user_reset();
//never reached
while(1);
}
}
• Assembly code is mandatory for the following sequence as Arm instructions need to be pipelined.
The assembler routine:
AREA TEST, CODE
INCLUDE AT91SAM9xxx.inc
EXPORTsoft_user_reset
soft_user_reset
;disable IRQs
MRS r0, CPSR
ORR r0, r0, #0x80
MSR CPSR_c, r0
;change refresh rate to block all data accesses
LDR r0, =AT91C_SDRAMC_TR
LDR r1, =1
STR r1, [r0]
;prepare power down command
LDR r0, =AT91C_SDRAMC_LPR
LDR r1, =2
;prepare proc_reset and periph_reset
LDR r2, =AT91C_RSTC_RCR
LDR r3, =0xA5000005
;perform power down command
STR r1, [r0]
;perform proc_reset and periph_reset (in the ARM pipeline)
STR r3, [r2]
END