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Subject: 
Re: 68hc11F1
Newsgroups: 
lugnet.robotics.handyboard
Date: 
Wed, 29 Jul 1998 07:13:02 GMT
Original-From: 
Richard meester <RICHARD.MEESTER@CHESS.avoidspamNL>
Viewed: 
1069 times
  
Hello mike,



Mike Davis wrote:

I am designing a board also.  I want a basic board with minimum I/O (for
small projects) and expansion connector to expanded I/O (for larger projects).
Two questions...

I also wanted a small board with MCU, memory, serial and a bus to the
outside world. This way i made a general io board and could connect
anything to it.

Hello Mike,

Sorry for the cryptical message,

I don't have a handyboard running at 16 Mhz, i made my own board,
currently with a 68hc11F1(@16Mhz), 32 K external RAM, 32k External

Is this the normal Crystal speed for the 11F1?  I was not aware that the
HC11 could run that fast.

You can buy the hc11F1 in 4 speeds, with a freq up to 16 Mhz, setting
the e-clock to 4. This gives 250 ns cycle time. In the ref. manual you
can find the mcu codes for the speeds, i don't know excact, but
something like 68hc11F1FN4

Also did you do anything special because of the
higher speed; like ground planes, etc.  Was this a PCB or wirewrapped?

My prototype is wirewrapped, i had some problems because of this, some
bad connections. Also you should take into account the cycle time.
Because during reads and writes during e-clock high you have 125 ns
timing. If you use decoded r/~w and ather system signals, you should
check the timing. I use a flash with 90 ns access time, and i also use a
74hct139 for system signal decoding (r/~w, E-clk).

flash. My programs are run from the flash, leaving aprox 32 k of stack
and heap. I also have a 50 pin header, to connect several other boards.
On this connector i have connected 2 * 4K of IO space, with chip select
lines. So i have 32k - 8k - 1k left for stack and heap. On this 2 * 4k
io space i'm designing a servo board, for rc hobby servos, 16 in total
with just 2 ICs. Another board i'm designing are H-bridges for 3 DC
motors. I'm thinking of designing 3 PIC micro's for the PID interface as
well as the encoder stuf and PWM stuf, and just interface to the PIC
with giving positions to move to and a start signal.

Since the HC11 only addresses 64K, and since there are internal resources
using some of that, how do you handle the overlap?

I think I asked more than two questions.

Thanks

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Hope this helps.



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