• A microprogram has a sequence of instructions in a microprogramming language.
– These are very simple instructions that specify micro‐operations.
Microprogrammed computers are characterized by the fact that the control signals are combined in control words, each bit of a word representing a control signal. The succession of the control words which indicate the correct sequence of elementary operations (micro-operations) that should be executed for each instruction is stored in a control memory. Each control word in the control memory represents a microinstruction, and it executes one or more micro-operations. The sequence of microinstructions form a microprogram.
A microprogrammed control unit has two main functions:
1. The control function, which defines the micro-operations that should be executed. This definition usually comprises the selection of the operands, selection of the operation to be executed, selection of the destination for a result, etc.
2. The sequencing function, which defines the address of the next microinstruction to be executed. This definition refers to identifying the source for the next address, controlling the test conditions, or generating the address value directly.
Micro‐instruction Types
• Each micro‐instruction specifies single (or few) micro‐operations to be performed
– (vertical micro‐programming)
• Each micro‐instruction specifies many different micro‐operations to be performed in parallel
– (horizontal micro‐programming)
More information
– These are very simple instructions that specify micro‐operations.
Microprogrammed computers are characterized by the fact that the control signals are combined in control words, each bit of a word representing a control signal. The succession of the control words which indicate the correct sequence of elementary operations (micro-operations) that should be executed for each instruction is stored in a control memory. Each control word in the control memory represents a microinstruction, and it executes one or more micro-operations. The sequence of microinstructions form a microprogram.
A microprogrammed control unit has two main functions:
1. The control function, which defines the micro-operations that should be executed. This definition usually comprises the selection of the operands, selection of the operation to be executed, selection of the destination for a result, etc.
2. The sequencing function, which defines the address of the next microinstruction to be executed. This definition refers to identifying the source for the next address, controlling the test conditions, or generating the address value directly.
Micro‐instruction Types
• Each micro‐instruction specifies single (or few) micro‐operations to be performed
– (vertical micro‐programming)
• Each micro‐instruction specifies many different micro‐operations to be performed in parallel
– (horizontal micro‐programming)
More information
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