ALU
[Hardware resources]

ALU connectivity:

Here it can be seen how the ALU plugs into the pipeline.

The ALU is a 100% combinational device.
It accepts 2 operands:

• a 16 bit operand
  This is taken through the Bypass Unit.
• an 8 bit operand
  This is taken through the Bypass Unit.

The ALU output is 16 bits wide.

ALU opcodes:

• NOP
  
• OP1
  Transfers operand 1 directly to the ALU output.
  OP2
  Transfers operand 2 directly to the lower 8 bits of ALU output.
  
• ADD8
  ADC8
  Adds with carry lower 8 bits of operand 1 with operand 2.
  SUB8
  SBC8
  
• AND8
  EOR8
  OR8
  
• INC8
  DEC8
  
• COM8
  NEG8
  SWAP8
  
• LSR8
  ASR8
  ROR8
  
• ADD16
  Adds without carry operand 1 with operand 2 sign extended to 16 bits.
  SUB16
  
• MUL8
  MULS8
  MULSU8
  FMUL8
  FMULS8
  FMULSU8
  

ALU flags:

• H (half carry)
• S (sign)
• V (two's complement)
• N (negative)
• Z (zero)
• C (carry)

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