Explain the Organization of micro-programmed control design.
Micr-program is a process of writing microcode for a microprocessor. Microcode is low-level code that defines how a microprocessor should function when it executes machine-language instructions. Typically, one machine language instruction translates into several microcode instruction, on some computers, the microcode is stored in ROM and can not be modified.
- A control unit with its binary control values stored as words in memory is called as micro programmed control. Each word in the control memory contains micro instruction that specifies one or more micro operations for the system. A sequence of micro instructions constitutes a micro program.
- Micro programmed implementation is a software approach in contrast to the hardwired approach.
- It deals with various units of software but at the micro level i.e. micro-operation, micro-instruction, micro-program etc.
- Different key elements used for implementation of a control unit using micro programmed approach is shown in fig. below:
Control Address Register (CAR)
It contains the address of next micro instruction to be read. This is similar to the program counter(PC) which stores the address of the next instruction.
Control Memory
The set of micro instruction is stored in control Memory (CM) also called as control store.
Control Buffer Register(CBR)
When microinstruction is read from the control memory, it is transferred to a control Buffer Register (CBR), which is similar to the instruction Register (IR) that stores the opcode of the instruction read from the memory.
Sequencing
It loads the control Address register with the address of the next instruction to be read abd issues a read command to control memory.
Post a Comment