A part answering at one address, with every register reading zero.
The address the part answers to.
How many transfers the part has served.
Marks bits of one register as the part's to set: a driver's write leaves them as the part holds them.
Puts a value in one register, read-only bits included, the way the part itself would.
What one register holds now, which is what a driver wrote there apart from the read-only bits.
A part that is not there, answering from 256 registers sixteen bits wide.
A pointer byte names a register and a register travels most significant byte first. A write of the pointer alone aims the next read; a write of the pointer and a word stores the word; a read takes words from the pointer on. Bits the part sets for itself, such as a conversion-ready flag, are marked with
readOnlyand keep the part's value whatever a driver writes.