Path: utzoo!attcan!uunet!mcsun!sunic!uupsi!rpi!brutus.cs.uiuc.edu!samsung!cs.utexas.edu!oakhill!tomj
From: tomj@oakhill.UUCP (Tom Johnson)
Newsgroups: comp.sys.m68k
Subject: Re: MC68HC000 Dissipation
Message-ID: <3076@oakhill.UUCP>
Date: 13 Mar 90 13:03:48 GMT
References: <760@cluster.cs.su.oz>
Reply-To: tomj@oakhill.UUCP (Tom Johnson)
Organization: Motorola Inc., Austin, Texas
Lines: 35

In article <760@cluster.cs.su.oz> jaa@cluster.cs.su.oz (James Ashton) writes:
>I have obtained an 8MHz CMOS version of the 68k.  As yet I have no data
>book for it but assume that it will comply with the specifications and
>in particular with the timing diagrams shown in my old standard 68k
>data book.  Could someone let me know if this is not the case.  Also,
>I'm assuming that power dissipation will be less than the 1.5 W rating
>of the standard 8MHz part.  If anyone could give me an idea of what
>typical dissipation might be with a 6MHz clock, I'd appeciate it.
>Meanwhile I'll get back to hunting down a data book for the beast.
>
>						James Ashton.

Yes, at 8, 10, & 12.5 MHz the timings of the 000 and HC000 are identical.
AT 16.67 MHz, the timings have some differences (with the HC000 having
better timings) because the "16MHz" 000 is actually a fast 12.5 MHz part
(i.e. specially screened).  This information is from rev 6 of the
68000 data book (available from your nearest Motorola Sales office).

Power dissipation is quite different:
	Clock	68000	68HC000
	-----	-----	-------
	8 MHz	~1.3W	0.13W
       10 MHz	~1.3W	0.16W
       12 MHz	~1.3W	0.19W
(these are for an ambient temperature of 25 deg. C - the 68000's Pd is
almost purely a function of temp).

Although Pd isn't given in the book for a 6 MHz speed (the part is allowed
to run as LOW as 4 MHz), Pd is relatively linear.  Thus, the difference
between 8 & 10 MHz will be roughly the same as the difference between 6 &
8 MHz (i.e. 0.03W).  Therefore, the Pd at 6 MHz should be close to 0.11W.

Hope this helps.

Tom Johnson	tomj@oakhill.UUCP