3.2. Bitwise Logic 2¶

3.2.1. EOR¶

The EOR instruction compares the individual bits of two patterns using logical exclusive or: produce a 1 if one of the two inputs is 1, produce 0 if the input bits are the same. In these two patterns:

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	1	0	1	1	0	0
0				0				0				0				0				0				A				C

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	1	1	1	0	1	1	0
0				0				0				0				0				0				F				6

Bits number 1, 3, 4, and 6 are 1 in exactly one of the inputs:

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	1	1	0	1	0
0				0				0				0				0				0				5				A

EORrd, rn, rm / #: Combine the bits of rn and the bits of rm or # with exclusive or. Result in rd.

3.2.2. NOT¶

Thgere is no instruction named NOT, but the MVN instruction does the job of logical NOT. It takes a pattern and flips all the bits so 1’s become 0’s and vice verse. This pattern:

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	0	1	0	1	0	1	1	0	0
0				0				0				0				0				0				A				C

Produces this when negated:

31	30	29	28	27	26	25	24	23	22	21	20	19	18	17	16	15	14	13	12	11	10	9	8	7	6	5	4	3	2	1	0
1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	1	0	1	0	1	0	0	1	1
F				F				F				F				F				F				5				3

MVNrd, rn / #: Place the bitwise negation of rm or # in rd. Does logical NOT.

@EOR gives 1 if bits are different
MOV   r7,      #0xac              @ r7 = 0000 ... 1010 1100
@              #0xFD                     0000 ... 1111 0110
EOR   r8, r7,  #0xFF              @ r8 = 0000 ... 0101 1010

MOV   r9,      #0xAC              @ r9 = 0000 ... 1010 1100
MVN   r10, r9                     @ r10= 1111 ... 0101 0011
MVN   r11, r10                    @ r11= 0000 ... 1010 1100

Try sample