1. Construct a controller of the process shown in the figure
Construct a controller of the process shown in the figure. The timer output (TU) is initially low when its input (TM) is low. When TM is taken high the output stays low for five minutes and then goes high. It resets to low when TM is taken low. All level sensors become true when the level is reached. The process sequence is:
Fill the tank to level A (LA) from valve A (VA)
Fill the tank to level B (LB) from valve B (VB)
Start the timer (TM), stir (S), and heater (H)
When five minutes are up take stir (S) and heater (H) off
Open output valve (VC) until the tank is empty (LE)
Take the timer low (TM) and go to step 1.

2. Solution;
To provide the solution, we first form the state variable representation of the system by assignment of binary states. There are four input variables (LA, LB, LE, TU) and six output variables (VA,VB,VC, TM, S, H). A discrete state of the system is defined by specifying these variables. Because each variable is a two-state variable, we use a binary representation: true=1 and false=0. Thus, for input, if level A has not been reached, then , LA=0 and if it has been reached, then LA=1. Also, for output, if valve C is to be closed, then we take VC=0, and if it is commanded to be open, then VC=1. Let us take the binary “word” describing the state of the system to be defined by bits in the order
Process outputs (Controller inputs): (LA)(LB)(LE) (TU)
Process inputs (Controller outputs): (VA)(VB)(VC)(TM)(S)(H)

3. Initial Condition (Stand By)
All outputs off
start LA VA 1 LB VB LU
S,TM,H LE VC

4. CAR 1 S 2 3 4 5 6 S0 S1 Control Outputs Control Memory (ROM) SEL
8 X 15
CAR 1 S 2 3 4 5 6
S0 S1
NXTADD1
NXTADD0
SEL
Control Outputs
Start

5. (VA)(VB)(VC)(TM)(S)(H)
Control Signals
• Six control signals needed.
• We can use these signals as is or encode
them to reduce the number of bits needed in
the control word.
• If we do not encode these: 6 bits needed
(VA)(VB)(VC)(TM)(S)(H)
VA:
VB:
VC:
TM:
S :
H :

7. -Register Transfer Description of the Microprogram
Each memory location contains a microinstruction, to be executed in the corresponding state. The register transfer statements are:

8. Address IniST: Start:CAR VAST, Start’ CAR İniST
The above Register Transfer Operation can be translated
into a symbolic microprogram (control words):
Example:
Address IniST: Start:CAR VAST, Start’ CAR İniST
can be written as:
Address IniST:

9. Symbolic Microprogram:
Address
NXTADD1
NXTADD0
SEL
CONTROL
IniST
VAST
Start
none
VBST LA VA
S;TM;HST LB VB
VCST TU
S, TM, H LE VC

10. Binary Microprogram