# Modbus function code 91

**URL:** <https://forums.digi.com/t/modbus-function-code-91/19421>\
**Category:** Digi One IA/IAP\
**Tags:** modbus\
**Created:** [April 24, 2018, 11:57am UTC](https://forums.digi.com/t/modbus-function-code-91/19421 "2018-04-24T11:57:36Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![enschot](https://avatars.discourse-cdn.com/v4/letter/e/e47774/32.png) [@enschot](https://forums.digi.com/u/enschot)\
**Post date:** [April 24, 2018, 11:57am UTC](https://forums.digi.com/t/modbus-function-code-91/19421/1 "2018-04-24T11:57:36Z")

</div>

Hello,

I need information about TCP/IP Modbus together with Function code 91 protocol or SEMI E54 communication protocol.  
I have already searched on internet but found almost noting.  
I need only the read function.  
How is the command build-up that is must send to my equipment.  
How is build-up the response that I receive back from my equipment.  
hopefully you can help me out.

best regards,  
Frans

---

<div class="post-metadata">

**Author:** ![Coralyn](https://avatars.discourse-cdn.com/v4/letter/c/e480ec/32.png) [@Coralyn](https://forums.digi.com/u/Coralyn)\
**Post date:** [July 18, 2018, 6:03am UTC](https://forums.digi.com/t/modbus-function-code-91/19421/2 "2018-07-18T06:03:58Z")

</div>

You won’t find any ‘standard’ docs on a function 91, because anything about 64 is ‘vendor specific’. Ultimately, the vendor selling the product needs to provide details.