Control A

Name:
CTRLA
Offset:
0x00 [ID-00001cd8]
Reset:
0x00000000
Access:
PAC Write-Protection, Write-Synchronized, Enable-Protected
Bit3130292827262524
Access
Reset
Bit2322212019181716
COPEN1COPEN0CAPTEN1CAPTEN0
AccessR/WR/WR/WR/W
Reset0000
Bit15141312111098
ALOCKPRESCALER[2:0]
AccessR/WR/WR/WR/W
Reset0000
Bit76543210
ONDEMANDRUNSTDBYPRESCSYNC[1:0]MODE[1:0]ENABLESWRST
AccessR/WR/WR/WR/WR/WR/WR/WR/W
Reset00000000

Bit 11 – ALOCK: Auto Lock

Auto Lock

When this bit is set, Lock bit update (LUPD) is set to '1' on each overflow/underflow or re-trigger event.

This bit is not synchronized.

ValueDescription
0 The LUPD bit is not affected on overflow/underflow, and re-trigger event.
1 The LUPD bit is set on each overflow/underflow or re-trigger event.

Bits 10:8 – PRESCALER[2:0]: Prescaler

Prescaler

These bits select the counter prescaler factor.

These bits are not synchronized.

ValueNameDescription
0x0 DIV1 Prescaler: GCLK_TC
0x1 DIV2 Prescaler: GCLK_TC/2
0x2 DIV4 Prescaler: GCLK_TC/4
0x3 DIV8 Prescaler: GCLK_TC/8
0x4 DIV16 Prescaler: GCLK_TC/16
0x5 DIV64 Prescaler: GCLK_TC/64
0x6 DIV256 Prescaler: GCLK_TC/256
0x7 DIV1024 Prescaler: GCLK_TC/1024

Bit 7 – ONDEMAND: Clock On Demand

Clock On Demand

This bit selects the clock requirements when the TC is stopped.

In standby mode, if the Run in Standby bit (CTRLA.RUNSTDBY) is '0', ONDEMAND is forced to '0'.

This bit is not synchronized.

ValueDescription
0 The On Demand is disabled. If On Demand is disabled, the TC will continue to request the clock when its operation is stopped (STATUS.STOP=1).
1 The On Demand is enabled. When On Demand is enabled, the stopped TC will not request the clock. The clock is requested when a software re-trigger command is applied or when an event with start/re-trigger action is detected.

Bit 6 – RUNSTDBY: Run in Standby

Run in Standby

This bit is used to keep the TC running in standby mode.

This bit is not synchronized.

ValueDescription
0 The TC is halted in standby.
1 The TC continues to run in standby.

Bits 5:4 – PRESCSYNC[1:0]: Prescaler and Counter Synchronization

Prescaler and Counter Synchronization

These bits select whether the counter should wrap around on the next GCLK_TCx clock or the next prescaled GCLK_TCx clock. It also makes it possible to reset the prescaler.

These bits are not synchronized.

ValueNameDescription
0x0 GCLK Reload or reset the counter on next generic clock
0x1 PRESC Reload or reset the counter on next prescaler clock
0x2 RESYNC Reload or reset the counter on next generic clock. Reset the prescaler counter
0x3 - Reserved

Bits 3:2 – MODE[1:0]: Timer Counter Mode

Timer Counter Mode

These bits select the counter mode.

These bits are not synchronized.

ValueNameDescription
0x0 COUNT16 Counter in 16-bit mode
0x1 COUNT8 Counter in 8-bit mode
0x2 COUNT32 Counter in 32-bit mode
0x3 - Reserved

Bit 1 – ENABLE: Enable

Enable

Due to synchronization, there is delay from writing CTRLA.ENABLE until the peripheral is enabled/disabled. The value written to CTRLA.ENABLE will read back immediately, and the ENABLE Synchronization Busy bit in the SYNCBUSY register (SYNCBUSY.ENABLE) will be set. SYNCBUSY.ENABLE will be cleared when the operation is complete.

ValueDescription
0 The peripheral is disabled.
1 The peripheral is enabled.

Bit 0 – SWRST: Software Reset

Software Reset

Writing a '0' to this bit has no effect.

Writing a '1' to this bit resets all registers in the TC, except DBGCTRL, to their initial state, and the TC will be disabled.

Writing a '1' to CTRLA.SWRST will always take precedence; all other writes in the same write-operation will be discarded.

Due to synchronization there is a delay from writing CTRLA.SWRST until the reset is complete. CTRLA.SWRST and SYNCBUSY.SWRST will both be cleared when the reset is complete.

ValueDescription
0 There is no reset operation ongoing.
1 The reset operation is ongoing.

Bits 20, 21 – COPEN: Capture On Pin x Enable [x = 1..0]

Capture On Pin x Enable [x = 1..0]

This bit selects the trigger source for capture operation, either events or I/O pin input.

ValueDescription
0 Event from Event System is selected as trigger source for capture operation on channel x.
1 I/O pin is selected as trigger source for capture operation on channel x.

Bits 16, 17 – CAPTEN: Capture Channel x Enable [x = 1..0]

Capture Channel x Enable [x = 1..0]

These bits are used to select whether channel x is a capture or a compare channel.

These bits are not synchronized.

ValueDescription
0 CAPTENx disables capture on channel x.
1 CAPTENx enables capture on channel x.