TNCF

Model

Note: Simic's built-in TCF is a fixed toggle flip-flop. It does not have an external T data input; it toggles on every active clock edge unless held by Set/Reset.

Operation

The TCF or TNCF toggles its state on the falling (negative) edge of C. Any prefix of these names can be used.

Note: TPCF is the T flip-flop with positive toggle, which triggers on the rising edge of C.

*Note: Set dominates when both NR and NS are low.

• TCF / TNCF: Negative-edge triggered (toggles on falling edge).
• TPCF: Positive-edge triggered (toggles on rising edge).

Timing Checks

Timing checks can be assigned by a TIMING-CHECKS block. Simic verifies the following constraints for TCF:

• SETUP: Specifies the duration that an input must be stable prior to the active clock edge (fall).
  • SETUP.NR: Setup from trailing edge of reset.
  • SETUP.NS: Setup from trailing edge of set.
• HOLD: Specifies the duration that an input must be stable after the active clock edge (fall).
  • HOLD.NR: Hold from reset.
  • HOLD.NS: Hold from set.
• PULSE-WIDTHS: Specifies the minimum width of a pulse on control lines.
  • PW.NR, PW.NS: Pulse-width reset/set.
  • PW.C.H, PW.C.L: High and low pulse-width clock.

Unspecified timing checks default to 0 (disabled).

Example Usage

part=FF1 type=TCF i=reset,set,clk o=q1 $
timing-checks= $
BEGIN; $
    SETUP = 5;      $ # All setups are 5 units
    HOLD = 5;       $ # All holds are 5
    PW = 4;         $ # All pulse-widths are 4
    PW.C.L = 3;     $ # Clock-low pulse-width is 3
END;

Equivalent Type Statement

Type=TNCF i=NR,NS,C o=Q
Type=TCF i=NR,NS,C o=Q

Note: TCF is an alias for TNCF.