# ANSI cross-coupled NAND latch

Canonical URL: https://eloragrid.ai/symbols/ansi-cross-coupled-nand-latch
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: S̄R̄
Drawing use: Schematic
Reference families: IEEE / ANSI, Manufacturer

## Symbol convention

Convention: IEEE / ANSI
Form: Two NAND outlines with each output fed back to the other gate's input
Distinctive-shape form as used in IEEE/ANSI-style schematics and manufacturer data books. Independent educational drawing; exact standard geometry and compliance are not asserted. The counterpart is the matching functional concept; no equivalence of every detailed standard graphic is asserted.
Related representation: [Set-reset latch](https://eloragrid.ai/symbols/set-reset-latch)

Two NAND gates with outputs fed back to each other, forming an SR latch with active-low set and reset.

## In plain English

### What does ANSI cross-coupled NAND latch mean?

Drawing the latch as two cross-coupled NAND gates shows its construction explicitly. A low on the set input forces Q high; a low on the reset input forces the complement high. With both inputs high the latch holds. Both inputs low drives both outputs high, which is normally treated as invalid.

### A simple example

This drawing form is common in teaching material, switch debounce circuits and older schematics where the latch is built from a quad NAND package. It lets a reviewer see the feedback paths and the pins used.

### What the drawings help you do

Because the latch is built from gates, the drawing shows nothing about which state it adopts at power-up. If a defined state is needed, a reset pulse or a pull network must be shown.

### This particular reference

Two NAND gates with outputs fed back to each other, forming an SR latch with active-low set and reset. The cross-coupled NOR latch has active-high inputs.

### Terms

- Signal: Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic: A drawing showing function and connections rather than physical appearance.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [SN74HC00 — NAND gate logic](https://www.ti.com/lit/ds/symlink/sn74hc00.pdf)
- [SN74LS279A — set-reset latches](https://www.ti.com/product/SN74LS279A)


## What it represents

Drawing the latch as two cross-coupled NAND gates shows its construction explicitly. A low on the set input forces Q high; a low on the reset input forces the complement high. With both inputs high the latch holds. Both inputs low drives both outputs high, which is normally treated as invalid.
This drawing form is common in teaching material, switch debounce circuits and older schematics where the latch is built from a quad NAND package. It lets a reviewer see the feedback paths and the pins used.
Because the latch is built from gates, the drawing shows nothing about which state it adopts at power-up. If a defined state is needed, a reset pulse or a pull network must be shown.

## How to read it

- Inputs are active low.
- Both inputs low gives both outputs high and is usually avoided.

## Information to show or reference

- Draw the feedback paths clearly without ambiguous crossings.
- Mark inputs as active low in the net names.
- Show any power-up reset arrangement.

## Important distinction

The cross-coupled NOR latch has active-high inputs.

## Facts

- Input sense: Active low
- Invalid state: Both inputs low
- Artwork scope: Original educational illustration; consult the applicable standard and the selected device documentation for the exact graphic

## Public references

- [SN74HC00 — NAND gate logic](https://www.ti.com/lit/ds/symlink/sn74hc00.pdf) — Texas Instruments. NAND gate documentation for the building block.
- [SN74LS279A — set-reset latches](https://www.ti.com/product/SN74LS279A) — Texas Instruments. SR latch device documentation.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.