Control Inputs
Data Input
Control Outputs
Status Signals
Data Output
The Control Unit
Control unit¡¯s job:
Supply all the control signals to the datapath
Respond appropriately to its status signals: Z, N, C, V
Control Unit
Control Signals
Datapath
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Von Neumann Architecture
Input to the control unit:
A stream of instructions coming from
memory M
This steam must be converted to a sequence of micro-operations for the datapath
Control Unit uses:
Program counter PC to index in M the next executable instruction
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Algorithmic State Machine
Data processing may be achieved through:
Sequencing Register transfer operations
May be specified as hardware algorithm Consists of a finite number of procedural steps
ASM are used: Control Unit Datapath
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ASM Chart
Algorithmic State Machine (ASM) Chart
Defines the hardware algorithm
Defines relation ship to time Clock
Three basic elements: State Box
Decision Box Conditional Output Box
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State Box contains:
State Box
Register transfer operation or output signals that are activated while the control unit is in this state.
RUN is 1 for any box it appears and 0 for any box it does not appear.
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False (0)
Decision Box
Exit path is taken if input condition is: True (1)
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Conditional Output Box
Conditional Output Box entry path must pass through one or more decision boxes.
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ASM Box Example
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ASM Block
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