Hex to Signed Decimal Conversion Rules
Given a Hex number, and you are told to convert to a signed integer (either as signed magnitude, 1s complement, 2s complement)
STEP 1: Determine the sign! If the Most Significant Bit is zero, the sign is positive. If the MSB is one, the sign is negative. This is true for ALL THREE representations: SM, 1s complement, 2s complement. $F0 = % 11110000 (MSB is ‘1’), so sign of result is ‘-’ $64 = % 01100100 (MSB is ‘0’), so sign of result is ‘+’.
If the Most Significant Hex Digit is > 7, then MSB = ‘1’ !!! (eg, $8,9,A,B,C,D,E,F => MSB = ‘1’ !!!)