Subject:
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68HC11 modes
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 12 Feb 1998 18:25:00 GMT
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Original-From:
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"Richard O'Neill [94094039-EE]" <RONEILL@THORUNG.ihatespamEENG.DCU.IE>
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Viewed:
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1367 times
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Date: Wed, 11 Feb 98 22:51 GMT
From: roneill ("Richard O'Neill [94094039-EE]")
To: roneill
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I read in the Motorola MC68HC11 reference manual that the hardware
mode select pins are "MODB" and "MODA" (pins 2 and 3). If the following
table is true (copied from the manual),
INPUTS MODE
MODB MODA DESCRIPTION
---------------------------------------
1 0 Normal single chip
1 1 Normal expanded
0 0 Special bootstrap
0 1 Special test
then, if MODB is always 0, the chip can only ever be in
Special Bootstrap or Special Test mode.
In the schematic of the CPU and Memory Circuit on the Handy Board
Web page, MODB is tied low, so how can the chip ever be in Normal
Single Chip mode?
thanks,
Rob O'Neill
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Message has 1 Reply:
 | | Re: 68HC11 modes
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| The handyboard has to stay in special test mode so that it can switch into and out of 'single chip' mode at will. This is necessary to operate the LCD (which uses either a clever or gross hack depending on your taste). If you are writing code using (...) (27 years ago, 14-Feb-98, to lugnet.robotics.handyboard)
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