17.3.1 Design Flow

The following steps are used to enable RTC in the application:

1. Enable RTC by using the MSS configurator in the application, as shown in the following figure.

   

2. Clicking RTC displays the RTC configuration window, as shown in the following figure.

   

   • Select the Clock Source that drives the RTC system (RTCCLK) as either External 32 KHz RTC crystal oscillator, or On-chip 1 MHz RC oscillator, or On-chip 25/50 MHz RC oscillator (50 MHz in 1.2V part). Irrespective of external main oscillator or RTC crystal oscillator selection, the auxiliary external oscillator is used as RTC clock source.
   • Select the Wake-Up Interrupt. The RTC_WAKEUP_CR in the SYSREG block provides masking for the RTC_WAKEUP interrupt to the FPGA fabric, the Cortex-M3 processor, and the system controller. The interrupt to be enabled can be selected using this configurator.
   • Select the RTC_MATCH. The RTC_MATCH status bit and output is asserted whenever the Alarm system is enabled and a match occurs. In Calendar mode, it is asserted for a 1 second period while the alarm condition is valid. The output is synchronous to the rising edge of the RTCCLK. The RTC_MATCH output signal can be exposed to drive the FPGA fabric. The RTC_MATCH signal is then available to be used in the design.
3. The RTC signals in top-level instance are shown in the following figure.

   

4. Generate the component by clicking Generate Component or by selecting SmartDesign > Generate Component. For more information on generation of the component, see the latest SmartDesign user guide on Libero SoC Documentation. The firmware driver folder and SoftConsole workspace is included in the project. Click the highlighted Configure firmware button as shown in the following figure to find the RTC drivers.

   

5. Click Generate Bitstream under Program Design to complete *.fdb file generation.
6. Double-click Export Firmware under Handoff Design for Firmware Development in the Libero SoC design flow window to generate the SoftConsole Firmware Project. The SoftConsole folder contains the mss_rtc firmware driver. The firmware driver, mss_rtc (mss_rtc.c and mss_rtc.h) which provides a set of functions for controlling the RTC, can also be downloaded from the Microchip firmware catalog. The following table lists the APIs for RTC. 
For more information on the APIs, see the SmartFusion2_MSS_RTC_Driver_UG (shown in the preceding figure).

   Table 17-3.  RTC APIs

   Category	API	Description and Usage
   Initialization	MSS_RTC_init()	Initializes RTC
   Setting and reading the RTC counter current value	MSS_RTC_set_calendar_count()	Sets new calendar values to RTC counter
   	MSS_RTC_set_binary_count()	Sets new binary values to RTC counter
   	MSS_RTC_get_calendar_count()	Returns calendar count
   	MSS_RTC_get_binary_count()	Returns binary counter value
   Setting the RTC match and mask values	MSS_RTC_set_calendar_count_alarm()	Sets the RTC to generate an alarm when the time and date passed as parameter
   	MSS_RTC_set_binary_count_alarm()	Sets the RTC to generate an alarm when the counter value passed as parameter
   RTC counter increment detection	MSS_RTC_get_update_flag	Indicates if the RTC counter incremented since the last call to MSS_RTC_clear_update_flag()
   	MSS_RTC_clear_update_flag	Clears the hardware flag set when the RTC counter increments
   Control of RTC	MSS_RTC_start()	Starts the RTC incrementing
   	MSS_RTC_stop()	Stops the RTC from incrementing
   	MSS_RTC_reset_counter()	Resets the calendar counters
   Interrupt control	MSS_RTC_enable_irq()	Enables the RTC wakeup interrupt
   	MSS_RTC_disable_irq()	Disables the RTC wake up interrupt
   	MSS_RTC_clear_irq()	Clears pending RTC wakeup interrupt

7. For more information on RTC usage, sample projects that are available can be generated, as shown in the following figure.