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_outpw

Posted on 1998-10-22
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I want to write on two 8 bit ports (like parallel) at the same time, one at address 0x600 and the other at address 0x601. I think to use _outpw(0x600, value). Is it right?
In what order is "value" copied?
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Question by:css
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by:arnond
ID: 1175736
It should work, the order depends on your code, which -outputw() is written first.
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by:css
ID: 1175737
I would like to find somebody who tryied that!!!
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bculver earned 1200 total points
ID: 1175738
The answer is Yes... doing an outpw(0x600,val) to an 8 bit device will do two sucessive writes, First write will be the low byte of val to address 0x600 the second write will be the hi byte of val to address 0x601. (Graphics programmers use this technic all the time to control the graphics controller chip.)

basically the i/o device sets the processers BS8 or BS16 pins to state its size 8 or 16 bit. the processer will automatically handle the rest using its BHE / BHL signals. If you want to know more details refer to a microprocessor manual and how the BS8/BS16 pins work and how the BHE and BHL signals are used as address line 0 on 8 bit devices.
 

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by:arnond
ID: 1175739
As I said, it works.
( I think the points should be mine...)
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