# Having problem with reading Modbus registers in a Micro 800 PLC **URL:** \ **Category:** Ignition\ **Created:** [October 7, 2022, 3:12pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952 "2022-10-07T15:12:26Z")\ **Posts on this page:** 16\ **Page:** 1
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 7, 2022, 3:12pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/1 "2022-10-07T15:12:26Z")
Followed the device setup, connected, created address registers, data is "bad". Although it appears it recognizes the register as valid. ![Screenshot 2022-10-07 111110](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/b/1b195711735bb6e9905990e498f7a2c7ce7872a1.png) ---
**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:** [October 7, 2022, 3:23pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/2 "2022-10-07T15:23:11Z")
Use "1" not "40001" for the address. ---
**Author:** ![andrews](https://avatars.discourse-cdn.com/v4/letter/a/898d66/32.png) [@andrews](https://forum.inductiveautomation.com/u/andrews)\ **Post date:** [October 9, 2022, 10:45am UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/3 "2022-10-09T10:45:03Z")
Following, cause I could never get them to work at my site. lol. ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 12, 2022, 6:12pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/4 "2022-10-12T18:12:59Z")
I have followed the tag setup and still get this. Its odd, I can see the tag values in quick client, and can actually change the PLC tag from the ignition screen I made. But tag is not working correctly acccording to this. [Screenshot 2022-10-12 121019|690x227](https://forum.inductiveautomation.com/uploads/short-url/pvHQCwx6SFJ9wMIW85svVUhdfFM.png) ---
**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:** [October 12, 2022, 6:15pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/5 "2022-10-12T18:15:08Z")
Do you have gaps in the Modbus addresses assigned to tags? If so, you will need to turn off the Ignition Driver's "span gaps" setting. ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 2:48pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/6 "2022-10-13T14:48:52Z")
After going through everything several times I still do not get quality data from source back to Ignition. I can write a value out to the modbus, but it does not read properly. Nothing I change has fixed this. This is to a Micro850 Allen Bradley PLC. See quality message in image. ![Screenshot 2022-10-13 104718](https://us1.discourse-cdn.com/inductiveautomation/original/3X/b/d/bd4641d31cf772bce485c1c508bc3004b6bb84ab.png) ---
**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:** [October 13, 2022, 2:52pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/7 "2022-10-13T14:52:03Z")
Show your driver settings for the `M850` device. Including the advanced settings. Have you tried including a node address? Like `[M850]1.HR1` ? Ignition's driver uses node zero if not given. ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 3:03pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/8 "2022-10-13T15:03:41Z")
![Screenshot 2022-10-13 110244](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/2/12058e8f1394d54d81fb3090cf832da0ed9a8608.png) ![Screenshot 2022-10-13 110223](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/c/fc32e225823b731a44b24fbebee011e47d01b497.png) ![Screenshot 2022-10-13 105958](https://us1.discourse-cdn.com/inductiveautomation/original/3X/1/7/173482409440a1c9c0bcd92f0925cd29db45e168.png) ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 3:04pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/9 "2022-10-13T15:04:30Z")
![Screenshot 2022-10-13 110410](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/5/f54ce3d8106e08976ee772e6acea851af53a9bd2.png) ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 3:05pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/10 "2022-10-13T15:05:41Z")
The strange thing is being able to write and change the variables in the 850. So I know it works one way. ---
**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:** [October 13, 2022, 3:37pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/11 "2022-10-13T15:37:54Z")
Turn "Span Gaps" _ **OFF** _, as I recommended above. ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 4:26pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/12 "2022-10-13T16:26:16Z")
Tried earlier with no luck, will try again. ---
**Author:** ![jay](https://avatars.discourse-cdn.com/v4/letter/j/ed8c4c/32.png) [@jay](https://forum.inductiveautomation.com/u/jay)\ **Post date:** [October 13, 2022, 5:06pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/13 "2022-10-13T17:06:02Z")
You do not need to define any addresses. ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/6/9/6976a7679bb328bd9d6c84226ffbd34b0e9d0788.png) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/d/3/d34681c30aacec9b24c808a7c1eb14590dbf9e18.png) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/b/1/b1fd3ebbc8608ece355d3f362d63038a4303e8aa.png) ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 5:09pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/14 "2022-10-13T17:09:20Z")
I have started over using a different method which works. But I still think the original method "Should" have worked. I created Modbus registers in the global tags table of the Micro850. Arrays 1-50 of coils and registers. In the user program I then map needed data from the source to these registers. In Ignition I read these register arrays instead of the source coil/int. Bi directional operation works. So I basically created a buffer for the data in the Micro. Nothing more. ---
**Author:** ![Calvin\_Johnson](https://avatars.discourse-cdn.com/v4/letter/c/aeb1de/32.png) [@Calvin\_Johnson](https://forum.inductiveautomation.com/u/Calvin_Johnson)\ **Post date:** [October 13, 2022, 5:14pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/15 "2022-10-13T17:14:13Z")
This is what I changed to. ![Screenshot 2022-10-13 131324](https://us1.discourse-cdn.com/inductiveautomation/original/3X/7/3/73ba293c9407866a4a0ed21a6d34a13456c4b3f0.png) ![Screenshot 2022-10-13 131300](https://us1.discourse-cdn.com/inductiveautomation/original/3X/2/1/21c0deace5dde2e70dd0dc17d7acbfb17c343b9e.png) ---
**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:** [January 4, 2023, 4:13pm UTC](https://forum.inductiveautomation.com/t/having-problem-with-reading-modbus-registers-in-a-micro-800-plc/64952/16 "2023-01-04T16:13:03Z")
Note that native access to ML8xx global tags (with some restrictions) is now available. Avoid the labor of setting up modbus on your tags: > [@Automation Professionals' EtherNet/IP Communication Suite V2](https://forum.inductiveautomation.com/t/automation-professionals-ethernet-ip-communication-suite-v2/68190): > > Automation Professionals is pleased to announce its latest EtherNet/IP Communications Suite driver module, a major upgrade to its EtherNet/IP Class1 Communications module, as a Public Beta. As of April 15, 2023, this is now a Production Release. The primary new feature is its new Generic EtherNet/IP Client Driver, a drop-in replacement for IA's Logix V21+ driver and its Omron NJ/NX driver. It does work with older Logix processors, and also works with Rockwell's MicroLogix 8xx family (ethernet…