BossEngineering Posted September 14, 2022 Report Share Posted September 14, 2022 The PLC is a Jazz2 JZ20-R31 with the latest firmware installed. I was attempting to switch from Ethernet communication to RS485. I used the parameters outlined in the U90 help file to code 2 ladder blocks to configure for modbus and also configure the RS485 adapter. I was unable to get the RS485 adapter working possibly due to incorrect parameters. Screen grabs of the 2 ladder blocks are attached. The problem is that I can no longer connect to the Jazz R31 through the built in USB port to correct any errors in programming. How can I re-establish the USB com port? Is there a way to reset to factory defults? Thanks in advance, Rob Quote Link to comment Share on other sites More sharing options...
MVP 2022 kratmel Posted September 14, 2022 MVP 2022 Report Share Posted September 14, 2022 You can try to set Jazz to STOP mode. Info mode must be used (via keyboard). Quote Link to comment Share on other sites More sharing options...
BossEngineering Posted September 14, 2022 Author Report Share Posted September 14, 2022 Thanks for the reply. I am familiar with info mode but how do I enter stop mode? Quote Link to comment Share on other sites More sharing options...
MVP 2022 kratmel Posted September 14, 2022 MVP 2022 Report Share Posted September 14, 2022 Info from Jazz manual Quote Link to comment Share on other sites More sharing options...
MVP 2014 Simon Posted September 15, 2022 MVP 2014 Report Share Posted September 15, 2022 Hi Rob, You can recover comms only by powering up the PLC into Stop mode. With power off hold down the (i) key while applying power. If you do a normal power up, as soon as the program starts it will configure the COM port and lock you out. If you then put it into stop mode from running mode, the COM port remains configured for Modbus. only. To prevent this from happening there is an alternative code for initialising Modbus. In your net 112 where you store #600 to SI140, change the #600 to #599. This allows the U90 ladder comments to be recognised by the PLC, even though the port is configurred for Modbus. Code #600 configures the port exclusively for Modbus and non-modbus comms are ignored. This is information is in the Modbus topic in the U90 ladder help. But I first found out about it the hard way, by being locked out of a PLC after downloading the program 🙂 1 Quote Link to comment Share on other sites More sharing options...
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