It isn't possible to address more than two PMCM1863 devices on one I2C bus because there is only one address line - so two devices are possible but no more.
However, there is another option:
In SPI mode the address input for I2C mode is the select input which is high for de-selected so if 3 out of 4 devices had this pin connected high they would respond to I2C on the higher address - however, it should then be possible to set the 4th device (let's call it the master), the one with address 0, to output three of its GPIO pins to the mode pins of the other 3 devices, the ones that have the address pin high in SPI mode.
If the GPIO output pin goes low then the device with the mode pin now set to zero will respond to I2C on the higher address - but no other.
Can someone confirm if the mode can be changed on the fly?
If so there is no limit to the number of devices one can use on the same I2C bus :o)
