# Modbus address with letter? **URL:** \ **Category:** Ignition\ **Tags:** ignition81\ **Created:** [December 4, 2023, 3:53pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665 "2023-12-04T15:53:24Z")\ **Posts on this page:** 14\ **Page:** 1
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 3:53pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/1 "2023-12-04T15:53:24Z")
How would I write 40110.b I get a format error with .b? Thank you in advance ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [December 4, 2023, 3:58pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/2 "2023-12-04T15:58:56Z")
`b` is supposed to be a digit, or pair of digits, that select a bit number from 0 to 15. Also, if the `4` indicates a holding register, you would replace that with `HR` on the Ignition side. So, `[someDevice]HR110.15` would yield a boolean for the high bit of that holding register. ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 4:06pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/3 "2023-12-04T16:06:48Z")
> [@pturmel](#): > > [someDevice]HR110.15 I tired to map like this ![map1](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/6/66887abe5f00f9c5c76c06b38460ce17cd41cbfe.png) But i can't connect to the device. I noticed it connected, but after i edited the mapping it just keeps disconnecting again. Any ideas? the .b should be a heartbeat. When it did connect a bad tag value. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 4:10pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/4 "2023-12-04T16:10:57Z")
> [@Barbara\_Frumas](#): > > the .b should be a heartbeat Not in this reality. Skip the address mapping. Review the address syntax in the [user manual](https://docs.inductiveautomation.com/display/DOC81/Modbus+Addressing). Consult the documentation you have for this device to figure out what address the "heartbeat" actually represents. ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 4:53pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/5 "2023-12-04T16:53:25Z")
No documentation for said device. Only info I have is whats already setup in the HMI program (advantech). I know device IP and registers, but thats it. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 4:55pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/6 "2023-12-04T16:55:14Z")
> [@Barbara\_Frumas](#): > > 40110.b This address, taken literally, doesn't mean anything outside of the system that invented that syntax. You've gotta figure out what it means to translate it to Ignition. Phil already probably guessed correctly that it's `HR110` as the base, but the `.b` is not obvious to me. ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 4:58pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/7 "2023-12-04T16:58:17Z")
any idea why I was only able to connect once to the device? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 4:59pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/8 "2023-12-04T16:59:28Z")
Often Modbus devices will close the connection if you read an invalid address, or don't read anything with in 10-15 seconds, or because you looked at them funny, or because the stars aren't aligned. The Ignition Gateway logs probably have some errors or warnings in them. ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 5:02pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/9 "2023-12-04T17:02:25Z")
Here is my log for warnings ![warn](https://us1.discourse-cdn.com/inductiveautomation/original/3X/7/b/7b118dbca3719ff8833c2014f0a7648b94093a93.png) ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [December 4, 2023, 5:03pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/10 "2023-12-04T17:03:51Z")
Well, that's the device telling you the address you're requesting is no good. Go back to the advice we both gave you earlier. No address map. Manually addressed tags. Read the manual for the syntax. Address `HR110`, not `HR40110`. ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 5:07pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/11 "2023-12-04T17:07:01Z")
Yeah no manual, trying to do a bit of reverse engineering i guess. ---
**Author:** ![dnsfontenot](https://avatars.discourse-cdn.com/v4/letter/d/b5ac83/32.png) [@dnsfontenot](https://forum.inductiveautomation.com/u/dnsfontenot)\ **Post date:** [December 4, 2023, 6:52pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/12 "2023-12-04T18:52:44Z")
Might try this configuration below. You need to add the device address.. This would get holding register 40028 bit 5 or 6 depending on your device being 0-15 or 1-16 bit based. [{ModemNum}]{DevAdd}.HR28.6 ---
**Author:** ![Barbara\_Frumas](https://avatars.discourse-cdn.com/v4/letter/b/94ad74/32.png) [@Barbara\_Frumas](https://forum.inductiveautomation.com/u/Barbara_Frumas)\ **Post date:** [December 4, 2023, 7:33pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/13 "2023-12-04T19:33:22Z")
what would ModemNum and DevAdd be? vs the above [devicename] ---
**Author:** ![dnsfontenot](https://avatars.discourse-cdn.com/v4/letter/d/b5ac83/32.png) [@dnsfontenot](https://forum.inductiveautomation.com/u/dnsfontenot)\ **Post date:** [December 4, 2023, 8:11pm UTC](https://forum.inductiveautomation.com/t/modbus-address-with-letter/82665/14 "2023-12-04T20:11:07Z")
> [@pturmel](#): > > [someDevice]HR110.15 I couldn’t get the modbus address configuration to work under the OPC UA, Device Connections section. So I mapped the device in the OPC Item Path… Mine are using parameters but yours would look like. [someDevice]1.HR110.15 Notice I had to add the 1 for the modbus device address if it's the first device. This allows the Device, then modbus device address, then the holding register then the bit to read. ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/b/d/bd2913d3217dd2625a4ebd7684adaa154a861d32.jpeg)