There were various revisions of the Multiface 2:
* There was a version which was visible to software all the time.(Did this exist?)
* One version had a "invisibility" switch on the front in addition to the stop and reset buttons. When switched in one direction the multiface was invisible to software and in the other it was visible. ''Is there a dump of the ROM from this version?''
* Last revision had an automatic "invisibility" switch internally controlled by the hardware itself. After reset the multiface was visible, but when the stop button was pressed and then control was returned to the running program it would be invisible and would remain invisible until the computer was reset.
The following applies to the automatic "invisibility" version (the "2+"):
If the multiface 2 is visible you can enable/disable the ROM and RAM in the CPU's address space:
The Multiface 2 listens to Gate-Array and PAL writes (port 7fxx), CRTC writes (bcxx and bdxx) and 8255 Control port writes (f7xx).
Gate-Array and PAL are decoded as 01111111xxxxxxxx, CRTC as 10111100xxxxxxxx and 10111101xxxxxxxx and 8255 writes as 11110111xxxxxxxx.
When the I/O write is detected, then specific locations in the MF2 RAM are updated immediately.