LZ: On subject of 2's complement format...
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LZ: On subject of 2's complement format...
IN>Okay... NEG results in the 2's complement of a number. This is
IN>basically the number*-1, if I am not mistaken. Can someone
IN>verify this instruction, as it would make my current project
IN>( a new driver for the temp sensor ) a lot easier when dealing
IN>with negative temperatures.
IN>BTW, does anyone have source code or notes from when Ed Plese
IN>wrote the original software? At this point, my remake can use
IN>multiple chip IDs and read a temperature. However, for some
IN>reason the chip gets locked on that temperature and won't change
IN>until I run Ed Plese's program. So somehow Ed wrote it to
IN>reset the LM75's onboard registers between reads. However, I
IN>don't know how he did it. Power-cycling the sensor does not work.
IN>I'm in desperation, almost ready to disassemble the original
IN>code to find out how he did it. ( At least I know that his read
IN>routines are near-exactly like mine, but HOW DID HE DO THE
IN>RESET? )
IN>Better yet, has anyone heard from him or Per Finander in the last
IN>year or so? From what I found, Ed wrote the software and the
IN>basic design while the latter created the I2C routines now available
IN>on TICALC.ORG and finished the final schematic of the sensor.
IN>Thanks for any help you can give.
IN>Ryan J. Myers ( Webmaster ) rmyers@inetarena.com (ICQ 1473314)
IN>Portland, Oregon ( US ) http://boris.inetarena.com/
IN>WWW Design, Z80 Assembly / Win95 Programming, CGI Scripting, 3D Graphics
IN>--------------------------------------------------------------------------
IN>The contents of this email are my own opinions and do not represent the
IN>positions of my employers unless specifically stated as such.
Here is an exact quote from "Programming the Z80" by Rodnay Zaks
On Page 358:
Description: Contents of the accumulator are subtracted from zero (two's
complement) and the result is stored back in the accumulator.
BTW the accumulator is register A
David