The datapath discussed previously was controlled by control signals. The following figure shows the structure of a simple control logic including two major components: (i) main control and (ii) ALU control.
- Main Control
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The main control sends the control signals to all components of a datapath except the ALU.
Its input and output are as follows:
- Input includes 6-bit opcode field from instruction.
- Output includes 10 control signals for the datapath.
- ALU Control
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As its name, the ALU control is to control the ALU.
Its input and output are as follows and details will be covered later.
- Input includes:
- 6-bit opcode field from instruction and
- 6-bit function (
funct) field from (R-type) instruction.
- Output includes a 4-bit
ALUctlsignal for ALU. Some of theALUctlis on the right.
- Input includes:
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You do not have to do this totally by the book (follow instructions exactly). |