Extended Precision Operations Little Endian vs Big Endian Which is ...

Signed Right Shift (>>)Signed Right Shift in PIC16 AssemblyThe value 0x80 = -128 in two’s complement.Recall that right shift is same as divide by two. Then-128 >> 1 == -128 / 2 == -64 == 0xC0If unsigned right shift is performed (0 shifted into MSB), then0x80 >> 1 == 0x40 == +64 , the wrong answer!!When doing a signed right shift, the MSB must be kept thesame value (this is also known as an arithmetic right shift).Makes sense, dividing a negative number by 2 should notchange the sign!!b7 b6 b5 b4 b3 b2 b1 b0C codesigned char i;i >> 1;Set carry to besame as sign bitbefore shift.PIC16 assembly;; i >> 1bcf STATUS,C ;clear carrybtfsc i,7 ;sign bit =1?bsf STATUS,C ;set carryrrf i ;i >> 1V 0.1 19V 0.1 20Signed Left Shift ( j true if i is to left of j,need for -i and +j to swap places if want to useunsigned comparison0xFF2560x80128-1280x7f127+127-1 -i +jSwap sides of -i, +j by complementing sign bits0x00000x0000V 0.1 23PIC16: Signed Comparison Algorithm #1Steps for i > j signed comparisonoperand adjustment1. Load j into w reg.2. Complement w sign bit by XOR’ing with 0x80.3. Store in temporary location (you pick), call this temp.4. Load i into w reg.5. Complement w sign bit by XOR’ing with 0x80.6. Subtract w from temp (new j -newi).Unsigned compare7. If carry = 0, then i > jV 0.1 244