# Modbus set digital output mask register

**URL:** <https://forum.universal-robots.com/t/modbus-set-digital-output-mask-register/18094>\
**Category:** Robot Communication\
**Created:** [December 9, 2021, 3:59pm UTC](https://forum.universal-robots.com/t/modbus-set-digital-output-mask-register/18094 "2021-12-09T15:59:51Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![malacasse1](https://avatars.discourse-cdn.com/v4/letter/m/eb9ed0/32.png) [@malacasse1](https://forum.universal-robots.com/u/malacasse1)\
**Post date:** [December 9, 2021, 3:59pm UTC](https://forum.universal-robots.com/t/modbus-set-digital-output-mask-register/18094/1 "2021-12-09T15:59:51Z")

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I wounder how works the Modbus output bit mask registers ?

Adress 1, Read/Write, Outputs  
Adress 2, Write, SetOutputsBitsMask  
Adress 3, Write, ClearOutputsBitsMask

In RTDE, there is a standard\_digital\_output\_mask to decide whether or not to control the digital output.  
I suppose it is a related function but I found no explicit documentation.