System

General Description

High level interface for interacting with reset and delays.

Features

This driver provides three categories of functionality:

• Ability to get the last reset reason.
• Ability to delay for a period of time.
• The ability to disable interrupts during a critical section.

Quick Start

• cyhal_system_critical_section_enter and cyhal_system_critical_section_exit are used to enable/disable global interrupts
• cyhal_system_delay_ms and cyhal_system_delay_us are delay functions used to halt the CPU exectution for a specified period of time
• cyhal_system_get_reset_reason gets the cause of latest system reset and cyhal_system_clear_reset_reason clears the reset cause registers

Code Snippets

Snippet 1: Critical Section

Critical section is a portion in the code where all active interrupts are disabled. This is usually provided in places where the code execution must not be disturbed by an interrupt. An example is a firmware controlled communication protocol where timing of each byte must be maintained and any interrupt might cause loss of data.
cyhal_system_critical_section_enter returns the current state of interrupts which denote the active interrupts in the system. This must be passed as argument to cyhal_system_critical_section_exit while exiting the critical section.

    /* Disables all interrupts */
    uint32_t state = cyhal_system_critical_section_enter();

    /* Application code where interrupts must be disabled */

    /* Re-enable all interrupts that were enabled before */
    cyhal_system_critical_section_exit(state);

Snippet 2: Reset reason

cyhal_system_get_reset_reason must be called at the beginning of the main to determine the reason for reset. The return parameters are present in cyhal_reset_reason_t.

    if (CYHAL_SYSTEM_RESET_WDT == cyhal_system_get_reset_reason())
    {
        /* WDT caused system reset */

        /* Application code to perform some action to indicate
         * that WDT caused the interrupt
         */

        /* Clear the reset reason */
        cyhal_system_clear_reset_reason();
    }
    else
    {
        /* Reset reason is not WDT
         * Could be POR or XRES.
         * Specify application code to perform some action to indicate
         * WDT was not the reset reaon
         */
    }

Enumerations
enum	cyhal_reset_reason_t {   CYHAL_SYSTEM_RESET_NONE = 0,   CYHAL_SYSTEM_RESET_WDT = 1 << 0,   CYHAL_SYSTEM_RESET_ACTIVE_FAULT = 1 << 1,   CYHAL_SYSTEM_RESET_DEEPSLEEP_FAULT = 1 << 2,   CYHAL_SYSTEM_RESET_SOFT = 1 << 3,   CYHAL_SYSTEM_RESET_HIB_WAKEUP = 1 << 4,   CYHAL_SYSTEM_RESET_WCO_ERR = 1 << 5,   CYHAL_SYSTEM_RESET_SYS_CLK_ERR = 1 << 6,   CYHAL_SYSTEM_RESET_PROTECTION = 1 << 7 }
	Flags enum of possible system reset causes. More...

Functions
uint32_t	cyhal_system_critical_section_enter (void)
	Enter a critical section. More...
void	cyhal_system_critical_section_exit (uint32_t old_state)
	Exit a critical section. More...
cy_rslt_t	cyhal_system_delay_ms (uint32_t milliseconds)
	Requests that the current operation delays for at least the specified length of time. More...
void	cyhal_system_delay_us (uint16_t microseconds)
	Requests that the current operation delay for at least the specified number of micro-seconds. More...
cyhal_reset_reason_t	cyhal_system_get_reset_reason (void)
	Gets the cause of the latest reset or resets that occurred in the system. More...
void	cyhal_system_clear_reset_reason (void)
	Clears the reset cause registers.

Enumeration Type Documentation

cyhal_reset_reason_t

enum cyhal_reset_reason_t

Flags enum of possible system reset causes.

Enumerator
CYHAL_SYSTEM_RESET_NONE	No cause.
CYHAL_SYSTEM_RESET_WDT	A watchdog timer (WDT) reset has occurred.
CYHAL_SYSTEM_RESET_ACTIVE_FAULT	The fault logging system requested a reset from its Active logic.
CYHAL_SYSTEM_RESET_DEEPSLEEP_FAULT	The fault logging system requested a reset from its Deep-Sleep logic.
CYHAL_SYSTEM_RESET_SOFT	The CPU requested a system reset through it's SYSRESETREQ.
CYHAL_SYSTEM_RESET_HIB_WAKEUP	A reset has occurred due to a a wakeup from hibernate power mode.
CYHAL_SYSTEM_RESET_WCO_ERR	A reset has occurred due to a watch-crystal clock error.
CYHAL_SYSTEM_RESET_SYS_CLK_ERR	A reset has occurred due to a system clock error.
CYHAL_SYSTEM_RESET_PROTECTION	A reset has occurred due to a protection violation.

Function Documentation

cyhal_system_critical_section_enter()

uint32_t cyhal_system_critical_section_enter

(

void

)

Enter a critical section.

Disables interrupts and returns a value indicating whether the interrupts were previously enabled.

Returns

Returns the state before entering the critical section. This value must be provided to cyhal_system_critical_section_exit() to properly restore the state

See Snippet 1: Critical Section for code snippet on critical section

cyhal_system_critical_section_exit()

void cyhal_system_critical_section_exit

(

uint32_t

old_state

)

Exit a critical section.

Re-enables the interrupts if they were enabled before cyhal_system_critical_section_enter() was called. The argument should be the value returned from cyhal_system_critical_section_enter().

Parameters

[in]

old_state

The state of interrupts from cyhal_system_critical_section_enter()

See Snippet 1: Critical Section for code snippet on critical section

cyhal_system_delay_ms()

cy_rslt_t cyhal_system_delay_ms

(

uint32_t

milliseconds

)

Requests that the current operation delays for at least the specified length of time.

If this is running in an RTOS aware environment (COMPONENTS+=RTOS_AWARE) or (DEFINES+=CY_RTOS_AWARE) it will attempt to have the RTOS suspend the current task so others can continue to run. If this is not run under an RTOS it will then defer to the standard system delay which is likely to be a busy loop. If this is part of an application that is build with RTOS awareness, but the delay should not depend on the RTOS for whatever reason, use cyhal_system_delay_us() with the appropriate 1000x multiplier to the delay time.

Parameters

[in]

milliseconds

The number of milliseconds to delay for

Returns

Returns CY_RSLT_SUCCESS if the delay request was successful, otherwise error

cyhal_system_delay_us()

void cyhal_system_delay_us

(

uint16_t

microseconds

)

Requests that the current operation delay for at least the specified number of micro-seconds.

This will generally keep the processor active in a loop for the specified length of time. If this is running under an RTOS, it will NOT attempt to run any other RTOS tasks, however if the scheduler or a high priority interrupt comes it they can take over anyway.

Parameters

[in]

microseconds

The number of micro-seconds to delay for

cyhal_system_get_reset_reason()

cyhal_reset_reason_t cyhal_system_get_reset_reason

(

void

)

Gets the cause of the latest reset or resets that occurred in the system.

Returns

Returns an enum of flags with the cause of the last reset(s)

Refer Snippet 2: Reset reason for code snippet on cyhal_system_get_reset_reason