1. ACCUMULATOR LOGIC
BY : SHIVAM BHARTI 

2. Inputs for Accumulator
 Set of 16 inputs come from the output of AC.
 Set of 16 inputs come from the output of DR.
 Set of 8 inputs come from the output of Input Register.
 The output of the adder and logic circuit provides the data input for the register.

3. Statements for Accumulator
 D0T5 : AC  AC ٨ DR AND with DR
 D1T5 : AC  AC + DR Add with DR
 D2T5 : AC  DR Transfer from DR
 pB11 : AC (0-7)  INPR Transfer from INPR
 rB9 : AC  AC Complement
 rB7 : AC  shr AC, AC (15)  E Shift right
 rB6 : AC  shl AC, AC (0)  E Shift left
 rB11 : AC  0 Clear
 rB5 : AC  AC +1 Increment

4. Circuits associated with Accumulator
Adder and logic
circuit
Accumulator register
Control gates
16
16
16
From DR
From INPR
16 16
LD
IN
R CLR
CLOCK

5. Control of AC Register
AccumulatorD0
T5
B9
D1
D2
r
B11
B7
B11
B5
B6
p
T5
AND
ADD
DR
INPR
COM
SHR
SHL
INC
CLR
16 16 to
BUS
clock
LD
INR CLR
From Adder and Logic

6. Control of AC Register……….
 The control function for the clear micro-operation is rB11 , where r = D7I’T3 and B11=IR(11).
 The output of the AND gate that generates this control function is connected to the CLR input of
the INR input of the register.
 The seven micro-operation are generated in the adder and logic circuit and are loaded into AC
at proper time.

7. Adder and Logic Circuit
 One stage of adder
and logic circuit

8. Stages of Adder and Logic circuit
 The adder and logic circuit can be sub-divided into 16 stages, with each bit corresponding to one
bit of AC.
 One stage of the adder and logic circuit consists of seven AND gates one OR gate and a full
adder (FA) as shown above.
 The input is labelled Ii output AC(i).
 When LD input is enabled, the 16 inputs Ii for i=0,1,2…15 are transferred to AC(i).
 The AND operation is achieved by AND ing AC(i) with the corresponding bit in DR(i).
 The transfer from INPR to AC is only for bits 0 through 7.
 The complement micro-operation is obtained by inverting the bit value in AC.
 Shift-right operation transfers bit from AC(i+1) and shift-left operation transfers the bit from AC(i-
1).
 The complete adder and logic circuit consists of 16 stages connected together.

9. Thanks………… 