1. EEE 4211 Microprocessor and I/O System
SAP-1

3. SAP-1 Timing Cycle for LDA Routine
Instruction T1 T2 T3 T4 T5 T6
LDA
Ep Lm’ Cp
Ce’ Li’
Ei’ Lm’
Ce’ La’ X
LDA T1 T2 T3 T4 T5 T6 Cp 1 Ep
Lm'
CE'
Li'
Ei'
La' Ea Su Eu
Lb'
Lo'

4. SAP-1 control Signals T1 T2 T3 T4 T5 T6 LDA ADD SUB OUT HLT Ep Lm’ Cp
Instruction T1 T2 T3 T4 T5 T6
LDA
Ep Lm’ Cp
Ce’ Li’
Ei’ Lm’
Ce’ La’ X
ADD
Ce’ Lb’
Eu La’
SUB
Su La’
OUT
Ea Lo’
HLT

5. State Equations Ep= T1 Cp= T2 Lm’= T1+ T4.LDA+T4.ADD+T4.SUB
Ce’= T3+ T5.LDA+T5.ADD+T5.SUB
Li’= T3
Ei’= T4.LDA+T4.ADD+T4.SUB
La’= T5.LDA+T6.ADD+T6.SUB
Ea= T4.OUT
Su= T6.SUB
Eu= T6.ADD
Lb’= T5.ADD+T5.SUB
Lo’= T4.OUT

6. Microprogramming Reduces the complexity of control circuit.
In Microprogramming, microinstructions are stored in a ROM instead of producing them with hardwired control matrix.

7. Construction of Microinstruction for SAP-1
For LDA, at t1, the states of control Signals are:
Cp=0 Ep=1 Lm=1 Ce=0 Li=0 Ei=0
La=0 Ea=0 Su=0 Eu=0 Lb=0 Lo=0
So the Controller has to generate the control word/ Microinstruction or 600h
In this way, microinstructions will be generated and stored in the control ROM.

8. SAP-1 Control ROM Address CON Routine Active 0H 5E3H Fetch Ep,Lm' 1H
Ep,Lm' 1H
BE3H Cp 2H
263H
CE',Li' 3H
1A3H
LDA
Lm',EI' 4H
2C3H
CE',La' 5H
3E3H
None 6H
ADD 7H
2E1H
CE',Lb' 8H
3C7H
La',Eu 9H
SUB AH BH
3CFH
La',Su,Eu CH
3F2H
OUT
Ea,Lo' DH EH FH X
NOT USED

9. SAP-1 Address ROM Address Contents Routine 0000 0011 LDA 0001 0110 ADD
0010
1001
SUB
XXXX
NONE
0100
0101
0111
1000
1010
1011
1100
1101
1110
OUT
1111

10. Microprogrammed Controller circuit
I7 I6 I5 I4
Address ROM
16X4 T3
Presettable
Counter
Load
CLOCK T1
CLR
CLR
Control ROM
12 bit

11. Implementation of HLT LDA Instruction Decoder 4-16 I7 I6 I5 i4 ADD SUB
OUT
HLT
CLK
Oscillator/
Clock Generator

12. What is the motivation behind Microprogramming
What is the motivation behind Microprogramming? With complete block diagram briefly explain the controller/sequencer design using microprogramming technique. Control word of the controller/sequencer is given.
Specify SAP-1 Control ROM and Address ROM contents.