presentation on micro programmed controlling.topic of somputer science architecture(csa) of sem 1 in delhi university.

1. Shashank Singh and Sarvesh Rawat

2. The control unit is a component of a
computer's central processing unit (CPU) which
directs operation of the processor. It controls
communication and co-ordination between
input/output devices. It reads and interprets
instructions and determine the sequence for
processing the data.

3.  Function of control unit
To initiate sequences of micro operations.
 Complexity of digital system
Is derived form the number of sequences
of micro operations that are performed.

5.  When the control signals are generated by
hardware using conventional logic design
techniques, the control unit is said to be
hardwired.
 Wiring change(if the design has to be
modified).
 Fast operations.

6.  The control information is stored in a
control memory, and the control memory is
programmed to initiate the required
sequence of micro operations.
 Any required change can be done by
updating the micro program in control
memory.
 Slow operations.

7. A control unit whose binary control
variables are stored in memory is called a
micro programmed control unit.
The control variables can be represented
by a string of 1’s and 0’s called a
control word.

9. Dynamic microprogramming
(Control Memory = RAM)
RAM can be used for writing (to change a
writable control memory) . Micro program is
loaded initially from an auxiliary memory such
as a magnetic disk.
Static microprogramming
(Control Memory = ROM)
Control words in ROM are made permanent
during the hardware production

10. Micro programmed control
Organization
Main memory
Stores user programs , contents of main memory can
be altered each time data is manipulated and every
time the program is changed.
Control memory
Stores a fixed micro program that cannot be altered by
the occasional user.

11. Next-
Address
Generator
(sequencer)
Control
Address
register
Control
Memory
(ROM)
Control
Data
register
Next address information
External input Control word

12. Control Address Register
Specify the address of the microinstruction
Sequencer(Next Address Generator)
Determine the address sequence that is read
from control memory . Next address of the next
microinstruction can be specified several way
depending on the sequencer input

13. Control Data Register
( Pipeline Register )
Hold the microinstruction read from control
memory.
Allows the execution of the micro operations
specified by the control word simultaneously
with the generation of the next
microinstruction.

15. Sequence of instructions
constitutes a program.
Data and instructions are
stored in main memory.
Can be altered by
occasional user.
 Sequence of micro
Instructions constitutes
a micro program.
 Data and micro instruction
Are stored in control memory
 Cannot be altered by
occasional user.