🚀 go-pugleaf

I have a question about an obscure point of the 16032's memory
management.  I'm aware that there is more recent documentation
than the stuff mentioned below, but the versions I have seen don't
shed any light on the matter.

	I have two documents describing the NS16032: a datasheet
	dated April 1982, and a manual about a year older.  The
	manual says that there are two restrictions on instruction
	restart after a memory-management abort:

	A. Cannot restart after aborting a write to a readonly page.
	B. Cannot restart an instruction with overlapping operands.

	The datasheet mentions neither of these restrictions, but
	does mention three of its own:

	1. If FLT hasn't been hit, the abort signal must strike
		before the end of Tmmu.
	2. If FLT has been hit, the abort signal must strike before
		FLT is turned off, and the abort will not be done
		until it's turned off.
	3. Read-modify-write accesses must never be aborted during
		the write part (the cpu helpfully provides enough
		information so you can catch them earlier).

	Since the manual did not deign to discuss electrical matters,
	it's no surprise that 1+2 were not mentioned there.  But A+B
	are rather different from 3.  Furthermore, the datasheet for
	the MMU does not mention whether it complies with ANY of 1-3.
	The definitions of one or two of its status bits do have an
	ominous sound, since they imply that R-M-W accesses can be
	aborted during the W part.  Does anybody know what the story
	is?  Surely the MMU must comply with 1+2 at least, but the
	datasheet I have says nothing about abort timing.  Compliance
	with 3 would be VERY NICE for the software, and the MMU does
	appear to have all the necessary information to do it right.

Replies by mail, please;  I will summarize for the net if there is
interest.

				Henry Spencer
				U of Toronto
				{allegra,ihnp4,linus,decvax}!utzoo!henry