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ALU
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ALU connectivity:
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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.
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ALU opcodes:
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- 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
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ALU flags:
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- H (half carry)
- S (sign)
- V (two's complement)
- N (negative)
- Z (zero)
- C (carry)
Generated on Sat Jul 3 08:13:38 2004 for Pipelined AVR microcontroller by
1.2.12 written by Dimitri van Heesch,
© 1997-2001