SiM3U1xx-power-mode-9

Introduction

  SiM3U1xx and SiM3C1xx devices have several power modes: Normal, Power Mode 1; Power Mode 2, Power Mode 3 Fast Wake, Power Mode 3, Power Mode 9(PM9). We will discuss PM9 in this documents.

Function Description

  In Power Mode 9, the core and all peripherals are halted, all clocks are stopped, and the pins and peripherals are set to a lower power mode. In addition, standard RAM contents are not preserved, though retention RAM contents are still available after exiting the power mode. This mode provides the lowest power consumption for the device, but requires an appropriate reset to exit. The available reset sources to wake from PM9 are controlled by the Power Management Unit (PMU).

To enter this mode, firmware should first set the PMSEL bit in the RSTSRC_CONFIG register to 1, and write the SLEEPDEEP bit in the ARM System Control Register. Firmware must then execute a WFI or WFE instruction. The core will remain in PM9 until an enabled reset source occurs.

The reset wake for PM9 can be sourced from pins (Pin Wake), the Low Power Timer, Comparator 0, RTC0 Alarms (0, 1, or 2), RTC0 Fail, or the Reset Pin (RESET). In most cases, the corresponding interrupt enable must be set in the module in order for an event to be a wakeup source. The Comparator module is the exception and the wakeup event will occur even if the interrupt is disabled. These wakeup sources (except for the reset pin) can also be optionally used to reset RTC0 or the Low Power Timer while the device remains in PM9.

Firmware can check the PM9EF bit during the initialization sequence to determine if the device reset because of a wake from Power Mode 9. If the device did reset because of a wake from PM9, firmware must clear the bits keeping the peripheral and pin interfaces in a lower power state (PERILPEN and PINLPEN), and the WAKESTATUS register provides status flags to indicate the wakeup source. The WAKESTATUS register can be cleared by writing 0 to the WAKECLR bit.

Code Implementation

   We made little modification in “Sleep” example code to realize PM9.

1.       Configured all port banks as desire function. (gPB.c)

void gPB_enter_default_config()

{

   // START APB CLK AND ENABLE SW PRINF

   SI32_CLKCTRL_A_enable_apb_to_modules_0(SI32_CLKCTRL_0, SI32_CLKCTRL_A_APBCLKG0_PB0);

   SI32_PBSTD_A_set_pins_push_pull_output (SI32_PBSTD_1, 0x00000008);

   // ENABLE CROSSBAR 1. WE WILL DRIVE LED's, SAMPLE BUTTONS, AND USE UART ON XBAR1

   SI32_PBCFG_A_enable_crossbar_1(SI32_PBCFG_0);

   // ENABLE LED DRIVERS (P2.10, P2.11) and turn on P2.10

   SI32_PBSTD_A_set_pins_push_pull_output(SI32_PBSTD_2, 0x00000C00);

   SI32_PBSTD_A_write_pins_low(SI32_PBSTD_2, 0x400);

   // ENABLE SWITCH SENSING (P2.10, P2.11)

   SI32_PBSTD_A_set_pins_digital_input(SI32_PBSTD_2, 0x00000300);

   // RTC PORT SETUP

   // RTC PINS TO ANALOG (PB0.9, PB0.10)

   SI32_PBSTD_A_set_pins_analog(SI32_PBSTD_0, 0x00000600);

   // BRING OUT RTC0 (PB2.7) (push-pull, P2.0-P2.6 skiped, RTC0 output enabled in crossbar)

   SI32_PBSTD_A_set_pins_push_pull_output(SI32_PBSTD_2, 0x00000080);

   SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_2, 0x0000007F);

   SI32_PBCFG_A_enable_xbar1_peripherals(SI32_PBCFG_0, SI32_PBCFG_A_XBAR1_RTC0EN);

   // UART PINS TO PROPER CONFIG (TX = PB1.12, RX = PB1.13)

   SI32_PBSTD_A_set_pins_push_pull_output(SI32_PBSTD_1, 0x0001000);   

   SI32_PBSTD_A_set_pins_digital_input(SI32_PBSTD_1, 0x00002000);

   SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_0, 0x0000FFFF);

   SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_1, 0x00000FFF);

   // BRING OUT UART

   SI32_PBCFG_A_enable_xbar0h_peripherals(SI32_PBCFG_0, SI32_PBCFG_A_XBAR0H_UART0EN);

}

2.       Added code to enter PM9. And added code to check reset source and wakeup source. Handle with exiting from PM9. (gPMU.c)

  // CHECK FOR POR

  if (SI32_PMU_A_is_power_on_reset_event_flag_set(SI32_PMU_0))

  {

     // IMMEDIATLY CLEAR POR SO ANY UNEXPECTED RESET WILL BE PROPERLY DECODED

     SI32_PMU_A_clear_por_flag(SI32_PMU_0);

     // SET VARIABLES

     reset_source = SI32_POWER_ON_RESET;

     wakeup_source = SI32_NO_WAKEUP;

     // APP BUILDER INSERTS USER FUNCTON OR DEFAULT FUNCTION HERE

     gModes_enter_my_default_mode();

     SI32_PMU_A_clear_pin_level_shifter_hold(SI32_PMU_0);

     return;

  }

  else if (SI32_PMU_A_is_wakeup_event_flag_set(SI32_PMU_0))

  {

    SI32_PMU_A_clear_wakeup_flags(SI32_PMU_0);

    reset_source = SI32_PMU_WAKEUP_RESET;

    wakeup_source = SI32_RESET_WAKEUP;

    gModes_enter_my_default_mode();

    SI32_PMU_A_clear_pin_level_shifter_hold(SI32_PMU_0);

    return;

  }

void pmu_sleep_now(void)

{

  // SAFTY CODE TO BE REMOVED LATER.

  // GROUNDING PB3.0 WILL CAUSE THE PART TO NOT GO TO SLEEP

  SI32_PBCFG_A_enable_crossbar_1(SI32_PBCFG_0);

  SI32_PBSTD_A_set_pins_digital_input(SI32_PBSTD_3, 0x00000001);

  if (SI32_PBSTD_A_read_pins(SI32_PBSTD_3) & 0x00000001)

  {

     // CLEAR WAKUP SOURCES

     SI32_PMU_A_clear_wakeup_flags(SI32_PMU_0);

     SI32_RSTSRC_A_enable_power_mode_9(SI32_RSTSRC_0);

     // SET DEEPSLEEP in SCR (and service all pending interrutps before sleep

     SCB->SCR = 0x14;

     __set_FAULTMASK(1);

     __WFI();

  }

}// pmu_sleep_now();

//------------------------------------------------------------------------------

void pmu_enter_sleep_till_reset_config(void)

{

   // DISABLE all wakeup sources

   SI32_PMU_A_write_wakeen(SI32_PMU_0, 0x0);

   // ENABLE Reset PIN as wake event

   SI32_PMU_A_enable_reset_pin_wake_event(SI32_PMU_0);

}

//------------------------------------------------------------------------------

void pmu_enter_sleep_till_alarm_config(void)

{

   // DISABLE all wakeup sources

   SI32_PMU_A_write_wakeen(SI32_PMU_0, 0x0);

   // ENABLE RTC_Alarm as wake event

   SI32_PMU_A_enable_rtc0_alarm_wake_event(SI32_PMU_0);

}

3.       Add RTC startup code, which needed by our PM9 reset source. (gRTC.c)

void gRtc0_enter_running_config(void)

{

   // ENABLE RTC CLOCK (+ IVC0 EXTVREG0 LPOSC0 EXTOSC0 LDO VREG0 VMON0)

   SI32_CLKCTRL_A_enable_apb_to_modules_1(SI32_CLKCTRL_0, SI32_CLKCTRL_A_APBCLKG1_MISC0);

   // SETUP RTC

   SI32_RTC_A_enable_module(SI32_RTC_0);

   SI32_RTC_A_enable_crystal_oscillator(SI32_RTC_0);

   SI32_RTC_A_set_clock_source_rtc(SI32_RTC_0);

   SI32_RTC_A_disable_bias_doubler(SI32_RTC_0);

   SI32_RTC_A_enable_autostep(SI32_RTC_0);

   SI32_RTC_A_enable_auto_gain_control(SI32_RTC_0);

   // START RTC AND WAIT FOR LOADCAP TO SETTLE

   SI32_RTC_A_start_timer(SI32_RTC_0);

   while(!SI32_RTC_A_is_load_capacitance_ready(SI32_RTC_0));

   SI32_RTC_A_clear_oscillator_fail_flag(SI32_RTC_0);

}

4.       Add code to check reset source and check retention ram and standard ram value.(main.c)

int main()

{

   // msTicks increments every 1ms (1Khz). Driven by boot osc (myCpu.c)

   // _last variables store the last seen state of variables so we know when they have changed

   uint32_t msTicks_last;

   // Keeps track of when button was depressed

   uint32_t hold_start = 0;

   uint32_t volatile *retention_ram = (uint32_t *)(0x20000000);

   uint32_t volatile *standard_ram = (uint32_t *)(0x20003000);

    // Setup the device in a mode depending on the reset/wakeup source

   setup_device();

   if (SI32_POWER_ON_RESET == get_pmu_reset_source())  {

     signal_POR();

     retention_ram[0] = 0x12345678;

     retention_ram[1] = 0xabcdef01;

   } else if (SI32_PIN_RESET == get_pmu_reset_source())  {

     signal_button_reset();

     while (SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 8));

     if((retention_ram[0] == 0x12345678) && (retention_ram[1] == 0xabcdef01)) {

       blink_3(0x800);

     } else  {

       blink_3(0x400);

     }

     while (SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 8));

     if((standard_ram[0] == 0x12345678) && (standard_ram[1] == 0xabcdef01))  {

       blink_3(0x800);

     } else {

       blink_3(0x400);

     }

   } else if (SI32_RESET_WAKEUP == get_pmu_wakeup_source())  {

     signal_reset_wake();

     while (SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 8));

     if((retention_ram[0] == 0x12345678) && (retention_ram[1] == 0xabcdef01))   {

       blink_3(0x800);

     }   else    {

       blink_3(0x400);

     }

     while (SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 8));

     if((standard_ram[0] == 0x12345678) && (standard_ram[1] == 0xabcdef01))  {

       blink_3(0x800);

     }  else   {

       blink_3(0x400);

     }

   } else  {

     //PANIC (TURN OFF LEDS AND SPIN)

     SI32_PBSTD_A_write_pb(SI32_PBSTD_2, 0xFFFF);

     while(1);

   }

   standard_ram[0] = 0x12345678;

   standard_ram[1] = 0xabcdef01;

   //PERFORM THE FOLLOWING TASKS FOREVER

   hold_start = 0;

   while (1)  {

      // If msTicks has changed

     if (get_msTicks() != msTicks_last)    {

         // IF PB2.9 BUTTON PRESSED

         if (!SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 9))  {

            // if start of button hold not logged then log it

            if(!hold_start)    {

               hold_start = get_msTicks();

            }

         }

         // IF BUTTON PB2.9 NOT PRESSED

         if (SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 9))      {

            // if the button was pressed

            if(hold_start > 0)     {

              sleep_for_ms(get_msTicks() - hold_start);

            }

         }

         // IF PB2.8 BUTTON PRESSED

         if (!SI32_PBSTD_A_read_pin(SI32_PBSTD_2, 8))      {

            // Sleep till reset pressed

            sleep_till_reset();

         }

         // save current msTicks value as last seen

         msTicks_last = get_msTicks();

      }// if msTicks changed

   }// while(1)

}// main()…

Function validation

      If POR occurs, both LEDs (DS3, DS4) will blink, we will store data in retention ram and standard ram. There are two options:When you press SW2(PB2.8), it will enter PM9 mode till reset; When you press SW3(PB2.9), it will enter PM9 mode till alarm, the alarm time is the time you press on SW3, and then wake up. Both option are turn on yellow LED(DS4) when enter PM9 mode.  

  If Reset wake occurs, yellow LED (DS4) will blink, it indicates exit from PM9.

  If button reset occurs, red LED (DS3) will blink, it indicates it is reset.

   Both above reset occur, we need to check retention ram and standard ram value.    First, Press SW2(PB2.8), it read out retention ram data and check whether it equal our preset value. If the value matched, it will blink yellow LED(DS4). If the value doesn't match, it will blink red LED(DS3). And then press SW2(PB2.8) again, it read out standard ram data check whether it equal our pre-set value.   If the value matched, it will blink yellow LED(DS4). If the value doesn't match, it will blink red LED(DS3). After checking ram data, we call choose two options by pressing SW2 or SW3.

References

1.       SiM3U1xx/SiM3C1xx Reference Manual: downloadable from the Silicon Labs web site at http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support Documents/TechnicalDocs/SiM3U1xx_SiM3C1xx_RM.pdf&src=DocumentationWebPart

2.       SiM3U1xx Data Sheet: downloadable from the Silicon Labs web site at http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support Documents/TechnicalDocs/SiM3U1xx.pdf&src=DocumentationWebPart

SiM3U1xx-current-mode-dac

Introduction

  SiM3U1xx and SiM3C1xx include current mode digital-to-analog converter (IDAC) module.  The IDAC takes a digital value as an input and outputs a proportional constant current on a pin.

Function Description

  The IDAC module includes the following features:   10-bit current DAC with output update trigger source options. Support for three full-scale output mode: 0.5, 1.0 and 2.0mA. Four-word FIFO to aid with high-speed waveform generation or DMA interactions.  Ability to update on rising, falling, or both edge for any of the external I/O trigger sources (DACnTx).

The various IDAC features and modes are enabled using the CONTROL register. There are four different modes: on-demand mode, periodic FIFO wrap mode, period FIFO-only mode, and periodic DMA mode.

  The IDAC full scale current output is configured using the OUTMD bit field. There are nominally 2.046, 1.023 and 0.5115 mA.

  Optionally, and on-chip load resistor can be enabled by setting the LOADEN bit. This enables an impedance path to ground which effectively produces a voltage at the output pin. 

IDAC conversions can be triggered “on-demand” with a write to the DATA register, or periodically using one of the internal timer options or external conversion trigger inputs.

We can have a look on below table for quick-reference on IDAC operation. That is very useful for setting up IDAC correctly. 

And here we have a look on IDAC electrical parameters in below table.

Code Implementation

   We used AppBuilder to generate basic code we need, and then added necessary code to make temperature sensor works.

1.       Enable clock of IDAC, DMA and Port bank module. (gCLKCTRL.c)

void CLKCTRL_setup_default_mode_clock_gates(void)

{

  SI32_CLKCTRL_A_enable_apb_to_modules_0(SI32_CLKCTRL_0,

                                         SI32_CLKCTRL_A_APBCLKG0_PB0 |

                                         SI32_CLKCTRL_A_APBCLKG0_TIMER0 |

                                         SI32_CLKCTRL_A_APBCLKG0_IDAC0);

  SI32_CLKCTRL_A_enable_ahb_to_dma_controller(SI32_CLKCTRL_0);

}

2.       Enable on-chip load resistor; set GAINADJ as 16, this value is well match with theory and measure result;  enable IDAC module; set output full-scale current output as 2mA ; and external trigger source use default setting which is PB3.2 with SiM3U1x7/C1x7 package.(gIDAC0.c)

void IDAC0_enter_default_mode_from_reset(void)

{

  SI32_IDAC_A_enable_load_resistor(SI32_IDAC_0);

  SI32_IDAC_A_set_output_fullscale_adjust(SI32_IDAC_0, 16);

  SI32_IDAC_A_enable_module(SI32_IDAC_0);

  SI32_IDAC_A_select_output_fullscale_2ma(SI32_IDAC_0);

}

3.       Port bank configuration. PB0.13 selected as IDAC0 output pin  need to be skipped in crossbar, P3.2  selected as external trigger source and need to be skipped in crossbar.(gPB.c)

void pb_enter_default_mode_from_reset(void)

{

  SI32_PBCFG_A_unlock_ports(SI32_PBCFG_0);

  // PB0 Setup

  SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_0, 0x2000);

  // PB1 Setup

  SI32_PBSTD_A_set_pins_push_pull_output(SI32_PBSTD_1, 0x0008);

  SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_1, 0x0008);

  // Enable Crossbar0 signals & set properties

  SI32_PBCFG_A_enable_crossbar_0(SI32_PBCFG_0);

  // PB2 Setup

  SI32_PBSTD_A_set_pins_push_pull_output(SI32_PBSTD_2, 0x0C00);

  SI32_PBSTD_A_set_pins_high_drive_strength(SI32_PBSTD_2, 0x0C00);

  // PB3 Setup

  SI32_PBSTD_A_write_pbskipen(SI32_PBSTD_3, 0x0004);

  // Enable Crossbar1 signals & set properties

  SI32_PBCFG_A_enable_crossbar_1(SI32_PBCFG_0);

}

4.       IDAC On-demand mode.

a.       Set output update trigger  with “the IDAC output updates on write to DATA (On Demand“, data format is single 10 bit and right-justified  as default setting.(myIDAC0.c)

void myIDAC0_enter_demand_mode(void)

{

  SI32_IDAC_A_set_output_update_trigger(SI32_IDAC_0,      SI32_IDAC_A_CONTROL_OUPDT_DACNT15_VALUE);

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x01F40190);

}

b.      Fetch data to IDACn_DATA register every 2 seconds, On-Demand mode, writes to this IDACn_DATA register update the IDAC value immediately, (main.c)

void IDAC0_demand_mode_fetch_data()

{

  uint32_t i, ms_ticks = 500;

  while (1) {

    for (i = 0; i < 1024; i += 100) {

      while (ms_ticks > get_msTicks()) {

      }

      ms_ticks = get_msTicks() + 2000;

      blink_led();

      printf("Output current is %d uA\n", fullscale_current * i / 1024);

      SI32_IDAC_A_write_data(SI32_IDAC_0, i);

    }

  }

}

5.       IDAC FIFO wrap mode

a.       Set data format as two 10 bit samples and right-justified; set the IDAC output updates on the falling edge of PB3.2; enabled FIFO wrap and reset FIFO before we access it.(myIDAC0.c)

void myIDAC0_enter_fifo_wrap_mode(void)

{

  SI32_IDAC_A_select_2x10bit_input_format(SI32_IDAC_0);

  SI32_IDAC_A_set_output_update_trigger(SI32_IDAC_0,  SI32_IDAC_A_CONTROL_OUPDT_DACNT13_VALUE);

  SI32_IDAC_A_enable_buffer_wrap(SI32_IDAC_0);

  SI32_IDAC_A_reset_buffer(SI32_IDAC_0);

}

b.      In this mode, the IDAC will continuously pull from the four-sample FIFO in a circular fashion. We only need to send data once to FIFO. Since we use two 10 bit samples format, for 4 words FIFO, we only need write two values to data register. (main.c)

void IDAC0_fifo_wrap_mode_fetch_data()

{

  // we set two 10 bit format, so we only need write data register twice

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x01F40190);

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x02BC0258);

  printf("P3.2 falling edge will trigger IDAC0 fifo wrap mode output\n");

}

6.       IDAC FIFO-only mode

a.        Set data format as single 10 bit sample and right-justified; set the IDAC output updates on the falling edge of PB3.2; Reset FIFO before we access it; enable FIFO went empty interrupt and 2^nd level interrupt handler function.(myIDAC0.c)

void myIDAC0_enter_fifo_only_mode(void)

{

  SI32_IDAC_A_set_output_update_trigger(SI32_IDAC_0, SI32_IDAC_A_CONTROL_OUPDT_DACNT13_VALUE);

  SI32_IDAC_A_reset_buffer(SI32_IDAC_0);

  SI32_IDAC_A_enable_buffer_went_empty_interrupt(SI32_IDAC_0);

  NVIC_ClearPendingIRQ(IDAC0_IRQn);

  NVIC_EnableIRQ(IDAC0_IRQn);

}

void IDAC0_empty_handler(void)

{

  int i;

  SI32_IDAC_A_clear_buffer_went_empty_interrupt(SI32_IDAC_0);

    for (i = 0; i < 4; i++) {

      idac_output_current = (idac_output_current + 100) & 0x3FF;

      SI32_IDAC_A_write_data(SI32_IDAC_0,idac_output_current);

    }

}

b.      In this mode, firmware will initiate a new write to the FIFO in went empty interrupt handler function. We still need to full fill FIFO when initialize IDAC module. (main.c)

void IDAC0_fifo_only_mode_fetch_data()

{

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x0190);

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x01F4);

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x0258);

  SI32_IDAC_A_write_data(SI32_IDAC_0, 0x02BC);

  printf("P3.2 falling edge will trigger IDAC0 fifo only mode output\n");

}

7.       IDAC DMA mode

a.       Set data format as single 10 bit sample and right-justified; set the IDAC ouput updates on the falling edge of PB3.2; Reset FIFO before we access it; enable FIFO interrupt and 2^nd level interrupt handler function (myIDAC0.c)

void myIDAC0_enter_dma_mode(void)

{

  SI32_IDAC_A_set_output_update_trigger(SI32_IDAC_0, SI32_IDAC_A_CONTROL_OUPDT_DACNT13_VALUE);

  SI32_IDAC_A_reset_buffer(SI32_IDAC_0);

  NVIC_ClearPendingIRQ(IDAC0_IRQn);

  NVIC_EnableIRQ(IDAC0_IRQn);

  idac_dma_mode_flag = 1;

}

void IDAC0_empty_handler(void)

{

  int i;

  SI32_IDAC_A_clear_buffer_went_empty_interrupt(SI32_IDAC_0);

  idac_dma_complete = 1;

  SI32_IDAC_A_disable_buffer_went_empty_interrupt(SI32_IDAC_0);

}

b.      Setup DMA base address; set DMA crossbar channel 3 as IDAC0 data request service; Enable the DMA channel; Setup DMA description configure, such as DMA count, DMA input data and destination endpoint. Enable DMA module; Start IDAC DMA transfer; Enable IDAC went empty interrupt. (myIDAC0.c)

void myIDAC0_initialize_dma_transfer(void)

{

  uint32_t ch;

  SI32_IDAC_A_reset_buffer(SI32_IDAC_0);

  printf("Initialize IDAC0 DMA transfer\n");

  SI32_DMACTRL_A_write_baseptr(SI32_DMACTRL_0, (uint32_t)desc_pri);

  ch = SI32_DMAXBAR_A_select_channel_peripheral(SI32_DMAXBAR_0, SI32_DMAXBAR_CHAN3_IDAC0);

  SI32_DMACTRL_A_enable_channel(SI32_DMACTRL_0, ch);

  SI32_DMADESC_A_configure(&desc_pri[3], idac_input_data, SI32_IDAC_0_TX_ENDPOINT, IDAC_DMA_COUNT, SI32_DMADESC_A_CONFIG_WORD_TX);

  SI32_DMACTRL_A_enable_module(SI32_DMACTRL_0);

  idac_dma_complete = 0;

  SI32_IDAC_A_start_dma_operation(SI32_IDAC_0);

  SI32_IDAC_A_clear_buffer_went_empty_interrupt(SI32_IDAC_0);

  SI32_IDAC_A_enable_buffer_went_empty_interrupt(SI32_IDAC_0);

}

c.       In this mode, we only need call DMA initialize function.(main.c)

void IDAC0_dma_mode_fetch_data()

{

  myIDAC0_initialize_dma_transfer();

  while (idac_dma_complete == 0) {

  }

  printf("IDAC dma mode transfer done!\n");

}

Function validation

1.        Use HP 34401A Multimeter, select DC current measurement function. Connect   wires to MCU CARD IDAC0(PB0.13) pin(in "ANALOG" area) and GND. 

2.        Connect a wire to PB3.2 pin with series-connected 1K resistor, we will connect another ends of the wire to generate falling edge event.   

3.       Download the code to a SiM3U1xx device on a SiM3U1xx MCU Card

4.       Run the code and use HP 34401A Multimeter observe the IDAC0 output constant current. For On-Demand mode, we can see output current value update in console windows in IDE every 2 seconds; For other modes, we need generate P3.2 falling edge event by pulling down voltage level, we can observe that output constant current change at each falling edge. 

References

1.       SiM3U1xx/SiM3C1xx Reference Manual: downloadable from the Silicon Labs web site at http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support Documents/TechnicalDocs/SiM3U1xx_SiM3C1xx_RM.pdf&src=DocumentationWebPart

2.       SiM3U1xx Data Sheet: downloadable from the Silicon Labs web site at http://www.silabs.com/pages/DownloadDoc.aspx?FILEURL=Support Documents/TechnicalDocs/SiM3U1xx.pdf&src=DocumentationWebPart