micro programmed control signal is the alternative technology of generating control signals inside the processor.

1. Micro programmed control

2. 3. Microprogram sequencing
• Microprogram is simple because std
software technique can be used.
• However, two major disadvantages may be
answered by this method.
• Separate microroutine for each machine
instruction cause large no of
microinstruction and large control store.

3. Contd.,
• Most machine instruction involve several
addressing mode.
• Many instruction of a processor have
different combinations of addressing modes.
• A separate microroutine for each of these
combinations would produce considerable
duplication of common parts.

4. • We should organize the microroutine so that
many common parts would share as
possible.
• [when it arise execution time is longer
because it takes more time to carry out the
required branches]

5. Example
–Add src, dst
the source operand can be specified in the
following addressing modes
1. Register
2. Auto increment
3. Auto decrement
4. indexed

7. 4. Microinstruction with next-Address field

8. 5. Prefetching microinstructions
One major drawback of microprogrammed
control is slower operating speed.bcoz of
fetching every micoinstruction from CS.
Prefetching of microinstruction facing some
operational difficulties that it must consider the
status flags and result of currently being
executed microinstruction.
Some time straight forward prefetches a wrong
microinstruction. Thus, the fetch must be
repeated with the correct address and it will
require more complex hardware.

9. 6.Emulation - Duplicate
• Additional instruction set.-Emulate the
function of one system to another so the
emulated machine reassembles the behavior
of real system.
• Programs written in the machine language
of M2 machine can then be run on computer
M1.

10. 6.Emulation - Duplicate
• Additional instruction set.-Emulate the
function of one system to another so the
emulated machine reassembles the behavior
of real system.
• Programs written in the machine language
of M2 machine can then be run on computer
M1.