28.6.2.4 Truth Table Inputs Selection

Input Overview

The inputs can be individually:

Masked
Driven by peripherals:
- Analog Comparator output (AC)
- Timer/Counters waveform outputs (TC)
- Serial Communication output transmit interface (SERCOM)
Driven by internal events from Event System
Driven by other CCL sub-modules

The Input Selection for each input ‘y’ of LUT x is configured by writing the Input ‘y’ Source Selection bit in the LUT x Control register (LUTCTRLx.INSELy).

Masked Inputs (MASK)

When a LUT input is masked (LUTCTRLx.INSELy = MASK), the corresponding TRUTH input (IN) is internally tied to zero, as illustrated in this figure.

Internal Feedback Inputs (FEEDBACK)

When selected (LUTCTRLx.INSELy = FEEDBACK), the Sequential (SEQ) output is used as input for the corresponding LUT.

The output from an internal sequential sub-module can be used as an input source for the LUT. See Figure 28-4 for an example for LUT0 and LUT1. The sequential selection for each LUT follows the formula:

I N [2 N] [i] = SEQ [N]

I N [2 N +1] [i] = SEQ [N]

With N representing the sequencer number and i = [0,1,2] representing the LUT input index.

For additional information, see Sequential Logic from Related Links.

Linked LUT (LINK)

When selected (LUTCTRLx.INSELy=LINK), the subsequent LUT output is used as the LUT input (for example, LUT1 is the input for LUT0), as illustrated in the following figure.

Internal Events Inputs Selection (EVENT)

Asynchronous events from the Event System can be used as an input selection, as illustrated in the following figure. For each LUT, one event input line is available and can be selected on each LUT input. Before enabling the event selection by writing LUTCTRLx.INSELy=EVENT, the Event System must be configured first.

By default, CCL includes an edge detector. When the event is received, an internal strobe is generated when a rising edge is detected. The pulse duration is one GCLK_CCL clock cycle.

I/O Pin Inputs (IO)

When the I/O pin is selected as the LUT input (LUTCTRLx.INSELy = IO), the corresponding LUT input is connected to the pin, as illustrated in the following figure.

Analog Comparator Inputs (AC)

The AC outputs can be used as an input source for the LUT (LUTCTRLx.INSELy=AC).

The analog comparator outputs are distributed following the formula:

I N [N] [i] = A C [N % C o m p a r a t o r O u t p u t_N u m b e r]

With N representing the LUT number and i = [0,1,2] representing the LUT input index.

Before selecting the comparator output, the AC must be configured first.

The output of comparator 0 is available on even LUTs ("LUT(2x)": LUT0) and the comparator 1 output is available on odd LUTs ("LUT(2x+1)": LUT1), as shown in the figure below.

The output of comparator 0 is available on even LUTs ("LUT(2x)": LUT0) and the comparator 1 output is available on odd LUTs ("LUT(2x+1)": LUT1), as illustrated in the following figure.

Timer/Counter Inputs (TC)

The TC waveform output WO[0] can be used as an input source for the LUT (LUTCTRLx.INSELy = TC). Only consecutive instances of the TC, that is, TCx and the subsequent TC(x+1), are available as default and alternative TC selections (for example, TC0 and TC1 are sources for LUT0, TC1 and TC2 are sources for LUT1). For an example for LUT0, see Figure 28-9. More generally, the Timer/Counter selection for each LUT follows the formula:

IN [N] [i] = D e f a u l t T C [N % TC_Instance_Number]

IN [N] [i] = A l t e r n a t i v e T C [(N + 1) % TC_Instance_Number]

Where N represents the LUT number and i represents the LUT input index (i=0,1,2).

Before selecting the waveform outputs, the TC must be configured first.

Timer/Counter for Control Application Inputs (TCC)

The TCC waveform outputs can be used as an input source for the LUT. Only WO[2:0] outputs can be selected and routed to the respective LUT input (that is, IN0 is connected to WO0, IN1 to WO1 and IN2 to WO2), as illustrated in the following figure.

The TCC selection for each LUT follows the formula:

IN [N] [i] = T C C [N % T C C_Instance_Number] . W O [i]

Where N represents the LUT number and i represents the LUT input index (i = [0,1,2]).

Before selecting the waveform outputs, the TCC must be configured first.

Serial Communication Output Transmit Inputs (SERCOM)

The serial engine transmitter output from the Serial Communication Interface (SERCOM TX, TXD for USART, MOSI for SPI) can be used as an input source for the LUT. The following figure illustrates an example for LUT0 and LUT1. The SERCOM selection for each LUT follows the formula:

IN [N] [i] = S E R C O M [N % SERCOM_Instance_Number]

With N representing the LUT number and i = [0,1,2] representing the LUT input index.

Before selecting the SERCOM as an input source, the SERCOM must be configured first: the SERCOM TX signal must be output on SERCOMn/pad[0], which serves as the input pad to the CCL.