Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!emory!gatech!prism!jkg
From: jkg@prism.gatech.EDU (Jim Greenlee)
Newsgroups: comp.sys.m68k
Subject: DTACK question
Message-ID: <16185@hydra.gatech.EDU>
Date: 1 Nov 90 03:47:05 GMT
Organization: Georgia Institute of Technology
Lines: 20

Can anybody tell me whether or not the 68000 family peripherals have
open-drain DTACK outputs? I'm mainly interested in the 68681, 68230, and
68901. Unfortunately, the M68000 Family Reference Manual isn't real clear
on this topic.

For example, the 68681 DTACK is described as a "three-state active low
open-drain output". The 68230 data section says that "a pullup resistor
is required to maintain DTACK high between bus cycles", which implies (to
me, anyway) that it is also open-drain. The 68901 DTACK is described only
as an "active low, three-state output".

It sure would simplify my life if they were all open-drain. Does anybody
know for sure?

						Jim Greenlee
-- 
Jim Greenlee - Instructor, School of ICS, Georgia Tech     jkg@cc.gatech.edu

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