Re: handyboard clock speed On Wed, 21 Apr 1999, Ian Nieves wrote:

> Ive checked the mailing list archives and i cant find a simple answer to the
> following question:
> Is it possible to run the HB at >2Mhz?  That is, can I run a different version of
> the 6811 perhaps and get 8Mhz?  What are the advantages/disadvantages?

From the data books for the 68HC11, if you have any version of the
E-series (except for perhaps one, a low-power version?), you can run them
at up to a 3MHz E-clock (12MHz crystal). 

I haven't looked at the rest of the handyboard schematic with that
objective in mind though.  It would require someone looking at the timing
in the datasheets for each component to determine whether it would work
reliably.  Perhaps Fred/Randy/Chuck may have looked at the circuit with
this in mind before?

I've been wondering that very same question lately though.  I have an E
processor in mine, and I would very much like to have an 50% speed
increase. 

I think the A-series processors are limited to a 2MHz E-clock.  I'm
running an E9 with the ROM disabled. 

The next question to ask is:  "Will my downloader work with the board
running at a different clock frequency?". 

I think this is how it works:  The HC11 starts downloading at 1200 baud
currently, and then switches to 9600 after getting the little 200-odd byte
downloader into the chip and running.  I'm not sure, but I think the chip
would start at 1800 baud for the first 200-odd bytes and then those
200-odd bytes that get loaded into the chip might need to be tweaked to
put the chip at a standard baud rate for the rest of the download. 

BTW:  I've now got interrupt-driven serial receive working in my
Handyboard GCC libraries, and I've also now tested the stepper motor code
on some real stepper motors.  I'll try to get the new library up on the
ftp site tonight.

Curt Mills, WE7U                         hacker.NO_*SPAM@tc.fluke.com
Senior Methods Engineer/SysAdmin
"Lotto:    A tax on people who are bad at math." -- unknown
"Windows:  Microsoft's tax on computer illiterates." -- WE7U


