---
name: "estop_latch"
section: "9"
platform: "linux"
package: "linuxcnc-uspace"
version: "1:2.9.4-2+deb13u1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/estop_latch"
---

# estop\_latch(9)

Software ESTOP latch

## NAME

estop\_latch - Software ESTOP latch

## SYNOPSIS

**loadrt estop\_latch \[count=*N*\|names=*name1*\[,*name2...*\]\]**

## DESCRIPTION

This component can be used as a part of a simple software ESTOP chain.

It has two states: "OK" and "Faulted".

The initial state is "Faulted".  When faulted, the **out-ok** output is false, the **fault-out** output is true, and the **watchdog** output is unchanging.

The state changes from "Faulted" to "OK" when **all** these conditions are true:

- •

  **fault-in** is false

- •

  **ok-in** is true

- •

  **reset** changes from false to true

When "OK", the **out-ok** output is true, the **fault-out** output is false, and the **watchdog** output is toggling.

The state changes from "OK" to "Faulted" when **any** of the following are true:

- •

  **fault-in** is true

- •

  **ok-in** is false

To facilitate using only a single fault source, **ok-in** and **fault-en** are both set to the non-fault-causing value when no signal is connected. For estop-latch to ever be able to signal a fault, at least one of these inputs must be connected.

Typically, an external fault or estop input is connected to **fault-in**, **iocontrol.0.user-request-enable** is connected to **reset**, and **ok-out** is connected to **iocontrol.0.emc-enable-in.**

**In more complex systems, it may be more appropriate to use classicladder to** **manage the software portion of the estop chain.**

## FUNCTIONS

- **estop-latch.***N*

  ## PINS

- **estop-latch.*N*.ok-in bit in (default: *true*)**

  - **estop-latch.*N*.fault-in bit in (default: *false*)**

  - **estop-latch.*N*.reset bit in**

  - **estop-latch.*N*.ok-out bit out (default: *false*)**

  - **estop-latch.*N*.fault-out bit out (default: *true*)**

  - **estop-latch.*N*.watchdog bit out**

  ## AUTHOR

John Kasunich

## LICENSE

GPL