Datasheet

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Name Description
Timer The timer/counter clock control is handled by an internal source
Counter The clock control is handled externally (e.g. counting external events)
CC For compare operations, the CC are referred to as “compare channels”
For capture operations, the CC are referred to as “capture channels.”
The counter in the TC can either count events from the Event System, or clock ticks of the GCLK_TCx
clock, which may be divided by the prescaler.
The counter value is passed to the CCx where it can be either compared to user-defined values or
captured.
The compare and capture registers (CCx) and counter register (COUNT) can be configured as 8-, 16- or
32-bit registers, with according MAX values. Mode settings determine the maximum range of the counter.
In 8-bit mode, Period Value (PER) is also available. The counter range and the operating frequency
determine the maximum time resolution achievable with the TC peripheral.
The TC can be set to count up or down. Under normal operation, the counter value is continuously
compared to the TOP or ZERO value to determine whether the counter has reached that value. On a
comparison match the TC can request DMA transactions, or generate interrupts or events for the Event
System. On a comparison match the TC can request DMA transactions, or generate interrupts or events
for the Event System.
In compare operation, the counter value is continuously compared to the values in the CCx registers. In
case of a match the TC can request DMA transactions, or generate interrupts or events for the Event
System. In waveform generator mode, these comparisons are used to set the waveform period or pulse
width.
Capture operation can be enabled to perform input signal period and pulse width measurements, or to
capture selectable edges from an internal event from Event System.
30.6.2 Basic Operation
30.6.2.1 Initialization
The following registers are enable-protected, meaning that they can only be written when the TC is
disabled (CTRLA.ENABLE =0):
• Control A register (CTRLA), except the Run Standby (RUNSTDBY), Enable (ENABLE) and
Software Reset (SWRST) bits
Enable-protected bits in the CTRLA register can be written at the same time as CTRLA.ENABLE is
written to '1', but not at the same time as CTRLA.ENABLE is written to '0'. Enable-protection is denoted
by the "Enable-Protected" property in the register description. The following bits are enable-protected:
• Event Action bits in the Event Control register (EVCTRL.EVACT)
Before enabling the TC, the peripheral must be configured by the following steps:
1. Enable the TC bus clock (CLK_TCx_APB).
2. Select 8-, 16- or 32-bit counter mode via the TC Mode bit group in the Control A register
(CTRLA.MODE). The default mode is 16-bit.
SAM D21 Family
TC – Timer/Counter
© 2018 Microchip Technology Inc.
Datasheet Complete
DS40001882D-page 666