The CY8CPLC10 device does not seem to respond to the I2C commands sent by an external I2C master. However, it responds correctly when using CY3240 I2C-USB Bridge and PLC control Panel as the I2C master. What could be a possible reason for this issue?
The minimum required "Bus Free Time Between a STOP and START Condition" for the I2C interface to CY8CPLC10 is 500 µs (as can be found in CY8CPLC10 device datasheet).
A violation of this specification has seen to be a common cause for communication failure between external master controllers and CY8CPLC10. Please verify if this specification is adhered to in your external master code.