Microprocessors

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Microprocessors

• Logical Operations Ch7

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ANL dest, source

• Logical AND for bytes.
• ANDs the bytes bit-by-bit.
• Binary zeros are used to MASK bits.
• Dest is usually A but may be direct address
• No effect on any flag.

A AND 0 0 A AND 1 A
0010 11010000 1011 mask 0000 1001
The mask.
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ANL C, source bit

• Logical AND for bits
• The CY flag is also called the Boolean
  Accumulator.

Sweet code because the jump happens if either
bit is low!
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ORL dest, source

• Logical OR for bytes
• ORs the bytes bit-by-bit.
• Dest is usually A but may be direct address
• No effect on any flag.

0000 01000110 1000 0110 1100
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ORL C

• Logical OR for bits
• The CY flag is also called the Boolean
  Accumulator.

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XRL dest, source

• Logical XOR for bytes
• XORs the bytes bit-by-bit.
• Dest is usually A but may be direct address
• No effect on any flag.
• Often used to clear a register (XRL A,A)
• Can be used with JZ to see if two registers have
  same value

0101 01000111 1000 0010 1100
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CPL A

• Complements each bit in a byte.
• Only works on accumulator.
• Used to produce 1s complement.

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CJNE A, source, dest

• Jump while A not equal to source
• Also CJNE Rn, source, dest
• Also CJNE _at_Ri, source, dest
• Source can be data or direct address.

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CLR A

• Clears accumulator with a one byte instruction.

To clear registers CLR A (one byte)MOV R0,
A (one byte)MOV R1, A (one byte)
Compare to MOV R0, 0 (two bytes)MOV R1,
0 (two bytes)
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RR A and RL A

• Adjusts the position of bit values in the
  accumulator.

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RRC A and RLC A

• Adjust the position of bit values in the
  accumulator and CY flag.

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SWAP A

• Exchange the upper nibble with the lower nibble.
• Works only on accumulator.

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Convert packed BCD to ASCII

• First it will be converted to unpacked BCD.
• Then the unpacked BCD is ORed to 30H.

• The following program converts packed BCD to
  ASCII.

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Start out with packed BCD.
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Save it for later.
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Mask the upper nibble.
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Stick on a 3 to make it ASCII.
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Stash the ASCII in R6
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Recall the original ASCII code.
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Mask the lower nibble.
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Rotate the upper nibble into the lower nibble.
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One SWAP instruction would to the same thing!
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Keep rotating.
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Keep rotating.
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Smack on the 3.
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Save it in R2. Done!
ASCII for 2 and for 9
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That's all folks!