D. Jay Newman | 22 Nov 20:08 2000

Re: two complement sum

> Somebody Knows why when using two complement sum of the pic ( and using Signed Aritimetic: bit 7 is the sign )
> adding 01  +  FF the result is "00" instead the correct "FE"
> and adding C0 + 60 the result is "60" instead the correct "20"
> And have a subroutine or to do this? (signed 2's complement sum"

1)
0x01 = 1
0xFF = -1

1 + -1 = 0

2)
0xC0 = 0b11000000
0x60 = 0b01100000

Since the low nibble is 0, we can look at
C = 1100
6 = 0110
   ------
    0010 + a carry bit

I get 0x20 for the answer, which may mean my binary is foggy.

Only in subtraction do you complement and add one.
--
D. Jay Newman           !
jay@...     ! Xander: Giles, don't make cave-slayer unhappy.
http://enerd.ws/robots/ !

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Denny Esterline | 23 Nov 19:57 2000
Picon

Re: [OT]: Pressure cooker burst disk ?

> So another way to ask this question would be: What pressure does a pressure
> cooking pot work at normally (assuming that the burst disk is set to give at
> that pressure times a safety factor).

The one we used to have for canning had three settings, 5, 10 and 15 PSI. 

-Denny

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