28.3.2.6 Sequential Logic

Each LUT pair can be connected to an internal Sequential block. A Sequential block can function as either D flip-flop, JK flip-flop, gated D-latch, or RS-latch. The function is selected by writing the Sequential Selection bits (SEQSEL) in the Sequential Control register (CCL.SEQCTRLn).

The Sequential block receives its input from either LUT, filter, or edge detector, depending on the configuration.

The Sequential block is clocked by the same clock as the corresponding LUT, which is either the peripheral clock or input line 2 (IN[2]). This is configured by the Clock Source bit (CLKSRC) in the LUT n Control A register (CCL.LUTnCTRLA).

When the even LUT (LUT0) is disabled, the latch is asynchronously cleared, during which the flip-flop Reset signal (R) is kept enabled for one clock cycle. In all other cases, the flip-flop output (OUT) is refreshed on the rising edge of the clock, as shown in the respective Characteristics tables.

Gated D Flip-Flop (DFF)

The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output (LUT1).

JK Flip-Flop (JK)

The J-input is driven by the even LUT output (LUT0), and the K-input is driven by the odd LUT output (LUT1).

Gated D-Latch (DLATCH)

The D-input is driven by the even LUT output (LUT0), and the G-input is driven by the odd LUT output (LUT1).

RS-Latch (RS)

The S-input is driven by the even LUT output (LUT0), and the R-input is driven by the odd LUT output (LUT1).