Timer 2

Description

Asynchronous timer with 4 capture/compare channels

The Timer 2 peripheral is a 16-bit timer that can operate at 24 MHz, 2 MHz or 32 kHz, independently of the Sensor Controller and other AUX domain functionality.

There are 4 capture/compare channels, which can be operated in one-shot mode or repeated mode. Each capture/compare channel can arbitrarily control the timer’s 4 event output signals. The following channel actions are supported:

  • Capture GPIO inputs or AUX event bus signals
  • Measure pulse width and interval
  • Clear or set event output(s) on 0, toggle event output(s) on compare
  • Clear, set, toggle or pulse event output(s) on compare

The 4 event output signals can be used:

  • Internally as:
    • Sensor Controller event handler code triggers
    • Timer 0 tick source
    • Timer 1 tick source
    • TDC start/stop trigger
    • ADC trigger
  • Externally as GPIO outputs, for example:
    • PWM
    • Power-up sequencing before Sensor Controller wake-up, and manually controlled power-down after measurements are done
    • Waveform generation

Block Diagram

The Timer 2 peripheral can be divided into four sections:

../_images/timer2__1__light.png

Clock Source Selection and Asynchronous Bus Bridge

The entire Timer 2 peripheral including hardware registers run off the selected clock. The following clock sources can be selected:

  • NONE
  • SCLK_HF/2 = 24 MHz (RCOSC or XOSC)
  • SCLK_MF = 2 MHz
  • SCLK_LF = 32 kHz (RCOSC or XOSC)

The default clock source is NONE. Only clock source selection is allowed in this state.

To enable use of Timer 2 (or change clock source), call timer2SetClockSource(src) to select SCLK_HF/2, SCLK_MF or SCLK_LF as the new clock source. Then call timer2WaitForClockSource() to wait for the clock switch to finish.

If Timer 2 shall be operated at SCLK_LF, it is recommended to perform configuration at a higher clock frequency:

  • Select SCLK_HF/2 if the Sensor Controller is in active mode, or SCLK_MF if the Sensor Controller is in low-power mode
  • Perform all Timer 2 configuration
  • Switch to SCLK_LF
  • Start Timer 2

The clock source selection affects the Timer 2 power consumption:

  • If SCLK_HF/2 is selected, the power supply system remains in active mode when the Sensor Controller returns to low-power or standby mode
  • When Timer 2 is no longer used, select NONE to eliminate Timer 2 power consumption.

Note that when Timer 2 runs off SCLK_HF or SCLK_LF, the clock will stop for a couple of clock cycles if the System CPU application switches between RCOSC and XOSC for that clock source. There are no such side-effects for SCLK_MF.

Counter

There is one 16-bit counter register. The counter can be operated in these modes:

  • Up once
  • Up repeatedly
  • Up and down repeatedly

The counter increments/decrements at the selected clock rate divided by the prescaler value.

  • Call timer2SetPrescaler(value) to set the prescaler value

The counter can increment from 0 to 65535, or from 0 to a variable target value.

  • Call timer2SetInitCounterTarget(value) to set the initial/current variable target value
  • Later while running, call timer2SetNextCounterTarget(value) to update the variable target value the next time the counter equals 0

For a target value 4, the counter increments as follows:

Up once 0 1 2 3 4                        
Up repeatedly 0 1 2 3 4 0 1 2 3 4 0 1 2 3 4 0 …
Up and down repeatedly 0 1 2 3 4 3 2 1 0 1 2 3 4 3 2 1 …

To start the counter, call timer2StartWithTarget(#mode) if using the variable target value, or call timer2Start(#mode) otherwise.

To stop the counter, call timer2Stop() .

The counter value can be accessed directly:

  • Call timer2SetCounter(value) to set the counter value
  • Call timer2GetCounter(value) to read the counter value

Capture/Compare Channels

There are 4 capture/compare channels. Each channel is identified by an index between 0 and 3.

Supported channel modes/actions ( TIMER2_CCMODE_XYZ ) and capture sources ( TIMER2_CAPTSRC_XYZ ) are listed in the constants table below. Note that only one channel can perform pulse width measurement at a time.

To use a channel in capture or pulse width/interval measurement mode:

  • Call timer2SetCaptSource(#chId, #source, #edge) to select capture source and signal edge
  • Call timer2CfgCcChannel(#chId, #modeAndAction, #bvEvIds) to select mode/action, and event outputs to be affected by this channel
  • After a capture has occurred, call timer2GetCaptValue(#chId; value) to read the capture value. The capture value is overwritten if another capture occurs before it is read.
  • After a pulse width/interval measurement has occurred, call timer2GetPulseMeas(#chId; pulseWidth, pulseInterval) to read the width and interval values

To use a channel in compare mode:

  • Call timer2SetInitCmpValue(#chId, value) to set the initial compare value
  • Call timer2CfgCcChannel(#chId, #modeAndAction, #bvEvIds) to select mode/action, and event outputs to be affected by this channel
  • Later while running, call timer2SetNextCmpValue(#chId, value) to update the compare value the next time the counter equals 0

To stop using a channel, call timer2ResetCcChannel(#chId) to reset all associated configuration and values.

Event Outputs

There are 4 event output signals. Each event output is identified by an index between 0 and 3.

The event outputs can be used as inputs to other Sensor Controller task resources, such as tick source for Timer 0/1, or trigger source for the ADC.

The event outputs can also be connected to I/O pins as follows:

  • Call timer2ConnectEventToGpio(#evId, auxio) to connect an event output to an output pin
  • To break the connection, call timer2DisconnectEventFromGpio(auxio)

In software it is possible to check the current event states or wait for a specific event state:

  • Call timer2GetEvents(bvEvIds) to get the state of each event, as a bit-vector
  • Call timer2WaitOnEvent(#evId, #level) to wait for a specific event output level

The event outputs can also be controlled manually:

  • Call timer2SetEvent(#evId) to set a single event output
  • Call timer2ClearEvent(#evId) to clear a single event output
  • Call timer2ModifyEvents(bvEvMod) to set or clear multiple event outputs simultaneously

Narrow Pulse Generator

The Timer 2 resource provides a narrow pulse generation feature that is only releated to the selected clock source.

Connect the TIMER2_EV_NARROW_PULSE event output to an I/O pin as described above. Then call timer2GenNarrowPulse() to output a pulse equal to the high part of one clock period.

Examples

32 kHz PWM Setup

// Select SCLK_MF temporarily as clock source to speed up Timer 2 register configuration. All
// register accesses occur at the selected clock rate.
timer2SetClockSource(TIMER2_CLOCKSRC_MF);
timer2WaitForClockSource();

// Configure Timer 2
timer2SetInitCounterTarget(cfg.counterTarget);

// Configure red LED Timer 2 channel
timer2ResetCcChannel(TIMER2_CH_RLED);
timer2CfgCcChannel(TIMER2_CH_RLED, TIMER2_CCMODE_SET_ON_0_TGL_ON_CMP, 1 << TIMER2_EV_ID0);
timer2SetInitCmpValue(TIMER2_CH_RLED, cfg.rledPwmValue);
timer2ConnectEventToGpio(TIMER2_EV_ID0, AUXIO_O_RLED_CTRL);

// Configure green LED Timer 2 channel
timer2ResetCcChannel(TIMER2_CH_GLED);
timer2CfgCcChannel(TIMER2_CH_GLED, TIMER2_CCMODE_SET_ON_0_TGL_ON_CMP, 1 << TIMER2_EV_ID1);
timer2SetInitCmpValue(TIMER2_CH_GLED, cfg.gledPwmValue);
timer2ConnectEventToGpio(TIMER2_EV_ID1, AUXIO_O_GLED_CTRL);

// Switch to SCLK_LF as clock source. PWM generation runs at this clock rate. There will only be
// one register access for each channel at this clock when we update the PWM values.
timer2SetClockSource(TIMER2_CLOCKSRC_LF);
timer2WaitForClockSource();

// Start Timer 2 in "count up repeatedly" mode
timer2StartWithTarget(TIMER2_CNTRMODE_UP_REP);

32 kHz PWM Update

// Update both channel compare values with the new PWM values
timer2SetNextCmpValue(TIMER2_CH_RLED, output.rledPwmValue);
timer2SetNextCmpValue(TIMER2_CH_GLED, output.gledPwmValue);

Procedures Overview

Name Brief description
fwClearManualEv() Clears the manual event signal, MANUAL_EV. More …
fwPulseManualEv() Pulses the manual event signal, MANUAL_EV (set for two SCE clock cycles, then cleared). More …
fwSetManualEv() Sets the manual event signal, MANUAL_EV. More …
timer2CfgCcChannel() Configures operation mode and event generation for a Timer 2 capture/compare channel. More …
timer2ClearEvent() Clears the specified Timer 2 event output. More …
timer2ConnectEventToGpio() Connects a Timer 2 event to a GPIO output pin (normal output, open-drain or open-source). More …
timer2DisconnectEventFromGpio() Disconnects any Timer 2 event from a GPIO output pin (output, open-drain or open-source). More …
timer2GenNarrowPulse() Generates a narrow pulse, one half of a Timer 2 clock period wide, on the TIMER2_EV_NARROW_PULSE event output. More …
timer2GetCaptValue() Returns the last capture value for a capture/compare channel. More …
timer2GetCounter() Returns the current Timer 2 counter value. More …
timer2GetEvents() Returns the state of each Timer 2 event output, one bit per event. More …
timer2GetPulseMeas() Returns the last capture/compare channel pulse width and interval measurement results. More …
timer2ModifyEvents() Sets or clears one or more Timer 2 event outputs. More …
timer2ResetCcChannel() Resets a Timer 2 capture/compare channel. More …
timer2SetCaptSource() Selects capture source and edge for a Timer 2 capture/compare channel. More …
timer2SetClockSource() Selects clock source for the Timer 2 counter. More …
timer2SetCounter() Sets the Timer 2 counter value. More …
timer2SetEvent() Sets the specified Timer 2 event output. More …
timer2SetInitCmpValue() Sets the initial compare value for a Timer 2 capture/compare channel. More …
timer2SetInitCounterTarget() Sets the initial target value for the Timer 2 counter. More …
timer2SetNextCmpValue() Sets the next compare value for a Timer 2 capture/compare channel. More …
timer2SetNextCounterTarget() Sets the next target value for the Timer 2 counter. More …
timer2SetPrescaler() Sets the Timer 2 prescaler division factor, between 1 and 256. More …
timer2Start() Starts Timer 2 without counter target value (equivalent to target value 65535). More …
timer2StartWithTarget() Starts Timer 2 with counter target value. More …
timer2Stop() Stops Timer 2. More …
timer2WaitForClockSource() Waits for any ongoing Timer 2 clock source switch to complete. More …
timer2WaitOnEvent() Waits for the specified level on a Timer 2 event. More …

Constants

Name Description
TIMER2_CAPTSRC_ADC_DONE Capture source: ADC measurement done
TIMER2_CAPTSRC_AON_BATMON_BAT_UPD Capture source: AON_BATMON battery voltage updated
TIMER2_CAPTSRC_AON_BATMON_TEMP_UPD Capture source: AON_BATMON temperature updated
TIMER2_CAPTSRC_AON_RTC_CH2 Capture source: AON_RTC channel 2 wake-up event
TIMER2_CAPTSRC_COMPA Capture source: COMPA output
TIMER2_CAPTSRC_COMPB Capture source: COMPB output
TIMER2_CAPTSRC_ISRC_RELEASE Capture source: ISRC release
TIMER2_CAPTSRC_MANUAL_EV Capture source: Manual event controlled by fwClearManualEv(), fwSetManualEv() and fwPulseManualEv()
TIMER2_CAPTSRC_MCU_EV Capture source: Event to the AUX domain from the MCU domain event fabric
TIMER2_CAPTSRC_SCLK_LF Capture source: SCLK_LF (32 kHz low-frequency clock)
TIMER2_CAPTSRC_SYS_ACTIVE Capture source: High while any part of the system (MCU domain, AUX domain and/or JTAG) is in active mode
TIMER2_CAPTSRC_TDC_DONE Capture source: TDC measurement done
TIMER2_CAPTSRC_TIMER0_EV Capture source: Timer 0 event
TIMER2_CAPTSRC_TIMER1_EV Capture source: Timer 1 event
TIMER2_CAPTSRC_VDDR_RECHARGE Capture source: VDDR recharge
TIMER2_CCMODE_CLR_ON_0_TGL_ON_CMP Continuous compare: Clear event(s) on 0, set event(s) on compare
TIMER2_CCMODE_CLR_ON_0_TGL_ON_CMP_DIS Single compare: Clear event(s) on 0, set event(s) on compare, then disable channel
TIMER2_CCMODE_CLR_ON_CMP Continuous compare: Clear event(s) on compare
TIMER2_CCMODE_CLR_ON_CMP_DIS Single compare: Clear event(s) on compare, then disable channel
TIMER2_CCMODE_DIS Disable channel
TIMER2_CCMODE_PER_PULSE_WIDTH_MEAS Continuous capture: Pulse width and interval measurement
TIMER2_CCMODE_PULSE_ON_CMP Continuous compare: Pulse event(s) for two clock cycles on compare
TIMER2_CCMODE_PULSE_ON_CMP_DIS Single compare: Pulse event(s) on compare, then disable channel
TIMER2_CCMODE_SET_ON_0_TGL_ON_CMP Continuous compare: Set event(s) on 0, clear event(s) on compare
TIMER2_CCMODE_SET_ON_0_TGL_ON_CMP_DIS Single compare: Set event(s) on 0, clear event(s) on compare, then disable channel
TIMER2_CCMODE_SET_ON_CAPT Continuous capture: Set event(s) on capture
TIMER2_CCMODE_SET_ON_CAPT_DIS Single capture: Set event(s) on capture, then disable channel
TIMER2_CCMODE_SET_ON_CMP Continuous compare: Set event(s) on compare
TIMER2_CCMODE_SET_ON_CMP_DIS Single compare: Set event(s) on compare, then disable channel
TIMER2_CCMODE_TGL_ON_CMP Continuous compare: Toggle event(s) on compare
TIMER2_CCMODE_TGL_ON_CMP_DIS Single compare: Toggle event(s) on compare, then disable channel
TIMER2_CLOCKSRC_HFDIV2 Clock source: SCLK_HF/2 (48 MHz / 2 = 24 MHz from XOSC or RCOSC)
TIMER2_CLOCKSRC_LF Clock source: SCLK_LF (32 kHz from XOSC or RCOSC)
TIMER2_CLOCKSRC_MF Clock source: SCLK_MF (2 MHz from RCOSC)
TIMER2_CLOCKSRC_NONE Clock source: No clock (Timer 2 inaccessible)
TIMER2_CNTRMODE_UP_DOWN_REP Counter mode: Up and down repeatedly
TIMER2_CNTRMODE_UP_ONCE Counter mode: Up once
TIMER2_CNTRMODE_UP_REP Counter mode: Up repeatedly
TIMER2_EV_ID0 Event output 0
TIMER2_EV_ID1 Event output 1
TIMER2_EV_ID2 Event output 2
TIMER2_EV_ID3 Event output 3
TIMER2_EV_NARROW_PULSE Event output pulsed by timer2GenNarrowPulse()

Global Variables

None.

Procedures

fwClearManualEv

Prototype: fwClearManualEv()

Clears the manual event signal, MANUAL_EV.

This event signal allows software to efficiently trigger:

  • TDC start/stop
  • Timer 2 capture

fwPulseManualEv

Prototype: fwPulseManualEv()

Pulses the manual event signal, MANUAL_EV (set for two SCE clock cycles, then cleared).

This event signal allows software to efficiently trigger:

  • TDC start/stop
  • Timer 2 capture

fwSetManualEv

Prototype: fwSetManualEv()

Sets the manual event signal, MANUAL_EV.

This event signal allows software to efficiently trigger:

  • TDC start/stop
  • Timer 2 capture

timer2CfgCcChannel

Prototype: timer2CfgCcChannel(#chId, #modeAndAction, #bvEvIds)

Configures operation mode and event generation for a Timer 2 capture/compare channel. This also allows the channel to be disabled.

The capture source and edge must be set (using timer2SetCaptSource() ) before enabling the channel in capture mode.

The compare value must be set (using timer2SetInitCmpValue() ) before enabling the channel in compare mode.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)
  • #modeAndAction : Channel mode selection and action performed on capture/compare (TIMER2_CCMODE_XYZ)
  • #bvEvIds : Capture/compare event generation mask (bit vector, one bit for each Timer 2 event (0-3))

timer2ClearEvent

Prototype: timer2ClearEvent(#evId)

Clears the specified Timer 2 event output.

Parameter value(s)

  • #evId : Event ID (0-3)

timer2ConnectEventToGpio

Prototype: timer2ConnectEventToGpio(#evId, auxio)

Connects a Timer 2 event to a GPIO output pin (normal output, open-drain or open-source).

Call this procedure multiple times to connect one Timer 2 event to multiple GPIO pins.

Call timer2DisconnectEventFromGpio() to break each connection.

Parameter value(s)

  • #evId : Event ID (0-3), or TIMER2_EV_NARROW_PULSE
  • auxio : GPIO output to be connected to the Timer 2 event (index of AUX I/O pin)

timer2DisconnectEventFromGpio

Prototype: timer2DisconnectEventFromGpio(auxio)

Disconnects any Timer 2 event from a GPIO output pin (output, open-drain or open-source).

Parameter value(s)

  • auxio : GPIO output to be disconnected from a Timer 2 event (index of AUX I/O pin)

timer2GenNarrowPulse

Prototype: timer2GenNarrowPulse()

Generates a narrow pulse, one half of a Timer 2 clock period wide, on the TIMER2_EV_NARROW_PULSE event output.

This functionality is not related to other Timer 2 functionality, and should not be confused with the pulse on compare channel actions.

Call timer2ConnectEventToGpio() to connect this event output to a GPIO output pin.

timer2GetCaptValue

Prototype: timer2GetCaptValue(#chId; value)

Returns the last capture value for a capture/compare channel.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)

Return value(s)

  • value : Timer 2 counter capture value

timer2GetCounter

Prototype: timer2GetCounter(value)

Returns the current Timer 2 counter value.

Return value(s)

  • value : Counter value

timer2GetEvents

Prototype: timer2GetEvents(bvEvIds)

Returns the state of each Timer 2 event output, one bit per event.

The event states are read simultaneously from the event bus. Note that due to synchronization delay, any event modifications by timer2ModifyEvents() , timer2SetEvent() or timer2ClearEvent() will not be captured by a back-to-back timer2GetEvents() call.

Return value(s)

  • bvEvIds : The state of each Timer 2 event output (bit N maps to event N)

timer2GetPulseMeas

Prototype: timer2GetPulseMeas(#chId; pulseWidth, pulseInterval)

Returns the last capture/compare channel pulse width and interval measurement results.

The capture/compare channel must be configured in TIMER2_CCMODE_PER_PULSE_WIDTH_MEAS mode.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)

Return value(s)

  • pulseWidth : Pulse width
  • pulseInterval : Pulse interval

timer2ModifyEvents

Prototype: timer2ModifyEvents(bvEvMod)

Sets or clears one or more Timer 2 event outputs.

Parameter value(s)

  • bvEvMod : Bit-vector indicating which events shall be cleared (bit 2N maps to event N) and set (bit 2N+1 maps to event N)

timer2ResetCcChannel

Prototype: timer2ResetCcChannel(#chId)

Resets a Timer 2 capture/compare channel.

This includes channel configuration, capture input source and capture/compare values.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)

timer2SetCaptSource

Prototype: timer2SetCaptSource(#chId, #source, #edge)

Selects capture source and edge for a Timer 2 capture/compare channel.

This procedure must be called before enabling a channel in capture mode.

To enable capture on a GPIO pin, the Digital Input Pins resource must be used.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)
  • #source : Capture source (AUXIO_I_XYZ or TIMER2_CAPTSRC_XYZ)
  • #edge : Edge that triggers capture (0 = falling edge, 1 = rising edge)

timer2SetClockSource

Prototype: timer2SetClockSource(src)

Selects clock source for the Timer 2 counter:

  • None (default)
  • SCLK_HF (24 MHz XOSC or RCOSC)
  • SCLK_MF (2 MHz RCOSC)
  • SCLK_LF (32 kHz XOSC or RCOSC)

Since most registers run on the selected clock, it is recommended to complete as much of the Timer 2 configuration as possible before switching to a slower clock source and starting the timer counter.

Use timer2WaitOnClockSwitch() to ensure that Timer 2 runs on the desired clock source.

Note that a small number of clock cycles are lost when SCLK_HF and SCLK_LF are switched between RCOSC and XOSC.

Parameter value(s)

  • src : Clock source (TIMER2_CLOCKSRC_XYZ)

timer2SetCounter

Prototype: timer2SetCounter(value)

Sets the Timer 2 counter value.

Parameter value(s)

  • value : New counter value

timer2SetEvent

Prototype: timer2SetEvent(#evId)

Sets the specified Timer 2 event output.

Parameter value(s)

  • #evId : Event ID (0-3)

timer2SetInitCmpValue

Prototype: timer2SetInitCmpValue(#chId, value)

Sets the initial compare value for a Timer 2 capture/compare channel.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)
  • value : Initial capture value

timer2SetInitCounterTarget

Prototype: timer2SetInitCounterTarget(value)

Sets the initial target value for the Timer 2 counter.

Parameter value(s)

  • value : Initial target value

timer2SetNextCmpValue

Prototype: timer2SetNextCmpValue(#chId, value)

Sets the next compare value for a Timer 2 capture/compare channel.

Parameter value(s)

  • #chId : Capture/compare channel ID (0-3)
  • value : Next capture value

timer2SetNextCounterTarget

Prototype: timer2SetNextCounterTarget(value)

Sets the next target value for the Timer 2 counter. This value takes effect after the currently used target value is reached.

This procedure must be called after timer2StartWithTarget() . Any calls while Timer 2 is stopped or is started without target have no effect.

Parameter value(s)

  • value : Next target value

timer2SetPrescaler

Prototype: timer2SetPrescaler(value)

Sets the Timer 2 prescaler division factor, between 1 and 256. The default value after chip reset is 1 (prescaler not used).

This procedure must be called before timer2Start() and timer2StartWithTarget() .

Parameter value(s)

  • value : New prescaler value

timer2Start

Prototype: timer2Start(#mode)

Starts Timer 2 without counter target value (equivalent to target value 65535).

The following counter modes are supported:

  • Up once
  • Up repeatedly
  • Up and down repeatedly

Parameter value(s)

  • #mode : Counter mode (TIMER2_CNTRMODE_XYZ)

timer2StartWithTarget

Prototype: timer2StartWithTarget(#mode)

Starts Timer 2 with counter target value.

The following counter modes are supported:

  • Up once
  • Up repeatedly
  • Up and down repeatedly

Call timer2SetInitCounterTarget() before timer2StartWithTarget() to set the initial counter target value.

Then, after calling timer2StartWithTarget() , call timer2SetNextCounterTarget() to change the counter target value if needed.

Parameter value(s)

  • #mode : Counter mode (TIMER2_CNTRMODE_XYZ)

timer2Stop

Prototype: timer2Stop()

Stops Timer 2.

timer2WaitForClockSource

Prototype: timer2WaitForClockSource()

Waits for any ongoing Timer 2 clock source switch to complete.

timer2WaitOnEvent

Prototype: timer2WaitOnEvent(#evId, #level)

Waits for the specified level on a Timer 2 event.

Note: A race condition can occur if this procedure is called before the previous Timer 2 procedure call has taken effect. This is particularly relevant if Timer 2 runs at a lower clock rate than the Sensor Controller.

Parameter value(s)

  • #evId : Event ID (0-3)
  • #level : Event level to wait for