The X-MASS is an ATA/IDE interface for the CPC made by ToTO. The device uses the same IDE I/O ports than the Symbiface 2 and is therefore compatible with it.
The device uses the same IDE I/O ports (except for the alternative status register and drive address register) than the Symbiface 2 and is therefore compatible with it. The port range it supports is FD08-FD0F. The device also has a Disk-On-Module IDE device connected. It This is connected as master and by default the X-MASS only supports a single device. It should be possible to remove this and use other compatible ATA devices. The X-MASS has a single device which is the master. It doesn't directly support a slave device unless with an adaptor is usedprovided they support 8-bit data transfer.
When the X-MASS is powered on the CPC is held in reset while the X-MASS communicates with the Disk-On-Module. If all is good the reset is released and the CPC starts up.
The I/O ports operate in a "pass-through" like mode where the registers directly reflect those of the connected ATA device.
Like the Symbiface 2, the device should be selected with port FD0E first, then the other I/O ports can be used to program the selected device.