1. ARM Bitwise Logic

2. Boolean Logic Identities
A or 1 = 1
Anything or'd with 1 is 1
A or 0 = A
Anything or'd with 0 is that thing
A and 1 = A
Anything and'd with 1 is that thing
A and 0 = 0
Anything and'd with 0 is 0
A xor 1 = not(A)
Xoring with 1 flips bit
A xor 0 = A
Xoring with 0 does nothing

3. Bitwise Logic
Bitwise operations : Work on patterns of bits, not values represented by those bits

4. Bitwise Logic
Bitwise OR:

5. Binary Immediates #0b starts a binary immediate value No spaces
Any 1’s must be in 8 consecutive bits 0b 0b 0b 0b

6. ORR
ORR: Bitwise OR ORR rd, rs, #___ ORR rd, rs, rm

7. AND
AND: Bitwise AND AND rd, rs, #___ AND rd, rs, rm

8. EOR
EOR: Bitwise exclusive OR EOR rd, rs, #___ EOR rd, rs, rm

9. Fun Fact
In Place Swap
EOR can swap two values in place

10. NOT
No NOT instruction – use MVN

11. BIC BIC: Binary Clear BIC rd, rs, #___ BIC rd, rs, rm
Clear bits set in # or rm

12. Bit Isolation Getting particular bits out of pattern Strategy 1:
Shift to wipe out others
Want to clear left 8 bits:
Shift left 8 bits:
Shift back right 8 bits:

13. Bit Isolation Getting particular bits out of pattern Strategy 1:
Shift to wipe out others
Want to isolate green five bits
Shift left 8 bits
Shift right

14. Bit Isolation Getting particular bits out of pattern Strategy 2:
Mask : binary pattern showing bits to keep

15. Using Masks AND with a 0 guantees 0 AND with 1, keeps other value:
Mask
Data
AND result

16. Hex Mask F (1111) mask a whole hex digit 0x0000000f Mask 0xfff00000
Data 0x
AND result 0x

17. Other Masks Sample mask patterns: 0x00 : keep no bits
0x01 : keep bit 0 ( )
0x04 : keep bit 2 ( )
0x05 : keep bit 0 & 2 ( )
0xC0 : keep bit 6-7 ( )

18. Bit Isolation Getting particular bits out of pattern Strategy 2:
Masking : binary pattern showing bits to keep
Want to keep just green bits
Create mask… 0x01F0 or 0b
AND

19. Mask Samples

20. High Level Code
In C/C++

21. High Level Code