Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!henry From: henry@utzoo.UUCP (Henry Spencer) Newsgroups: net.micro.16k Subject: 16032 MMU query Message-ID: <3062@utzoo.UUCP> Date: Sat, 2-Jul-83 01:10:47 EDT Article-I.D.: utzoo.3062 Posted: Sat Jul 2 01:10:47 1983 Date-Received: Sat, 2-Jul-83 01:10:47 EDT Organization: U of Toronto Zoology Lines: 43 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