jaa@cluster.cs.su.oz (James Ashton) (03/12/90)
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.
tomj@oakhill.UUCP (Tom Johnson) (03/13/90)
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