First,you need to change I-7550 PROFIBUS address to 126, then you can use "set PROFIBUS address" function of PROFIBUS master to change I-7550 PROFIBUS address.
Please refer to the following step.
1. set dip switch to 255 and power up I-7550.
2. set dip switch to 126 and reset I-7550.(now the PROFIBUS address of I-7550 is 126)
3. Use "set slave address" function of PROFIBUS master to set I-7550 PROFIBUS address, I-7550 will store the slave address to EEPROM.
Please note that it can only set one device at the same time.