While the B rev part is usually cheaper and has fixes to the errata you
still need to be careful when changing to the newer silicon. You may find
the oscillator startup has changed and you may need to change your cap
values on the crystal. You may also see a slightly narrower voltage rating
as higher voltages are harder with smaller geometries. Another thing is the
robustness. Sometimes we tend to run beyond the ratings and I have seen
some of the older revisions prior to die shrinks that seem to run fine
beyond published specs where the newer die shrink can't be pushed as far.
Always test the new silicon in your application. If you obey the rules and
stay within the data sheet specifications you probably won't have problems.

Larry



At 09:50 PM 4/8/00 -0400, you wrote:
>I guess I have myself to blame.  I didn't know that there were B parts when I
>ordered them and I didn't ask.  I will be sure to ask what the latest
>revisions are next time.  Kind of surprises me that FAI still had A parts.  I
>would think their inventory moves pretty fast.
>
>Jim Robertson wrote:
>
>> At 07:27 PM 4/8/00 -0400, you wrote:
>>
>> The 74B parts have the BRGH = 1 bug fixed and would most likely have been
>> cheaper. You got less for more in all likelyhood. I would ask for their
>> 74B price to compare.
>>
>> There is a real grey area here with their ethics IMHO.
>>
>> Jim
>>
>> >I just checked the M'chip site and noticed that there is a 16C74B.  I
>> >just bought a bunch of 74A parts from FAI a few days ago.  Can anyone
>> >tell me if there are problems with the 74A.  Did I get stuck with old
>> >stock that they couldn't sell to anyone else?
>> >
>> >Dan Michaels wrote:
>> >
>> >> Tom McGahee wrote:
>> >> >Dear PICSTERS,
>> >> >I am in the middle of a project using a PIC16C74 and I
>> >> >am having trouble getting my routines that use the
>> >> >built-in Asynchronous Receiver/Transmitter to work.
>> >> >
>> >> >Part of the problem is that there are inconsistencies and
>> >> >errors in the manual for this device. The other part of the
>> >> >problem is that the manual has no sample initialization
>> >> >routines and sample serial input and output routines.
>> >> >
>> >>
>> >> Some of the older '74 chips had UART h.w. problems.
>> >> You might check the Mchp errata page for the latest.
>> >
>> Regards,
>>
>> Jim Robertson
>> NEWFOUND ELECTRONICS
>> ________________________________________
>> Email: newfound@pipeline.com.au
>> http://www.new-elect.com
>> MPLAB compatible PIC programmers.
>> ________________________________________
>
>
Larry G. Nelson Sr.
mailto:L.Nelson@ieee.org
http://www.ultranet.com/~nr