Digital Electronics Notes - Kalinga University - DICS 302

**KALINGA UNIVERSITY** **DEPARTMENT OF ELECTRICAL ENGINEERING** **Subject: Digital Electronics** **Subject Code: DICS 302** **Course: DICS Semester-3^rd^** **UNIT-IV** Digital Circuits - Counters =========================== - Asynchronous counters - Synchronous counters Asynchronous Cou...

**KALINGA UNIVERSITY** **DEPARTMENT OF ELECTRICAL ENGINEERING** **Subject: Digital Electronics** **Subject Code: DICS 302** **Course: DICS Semester-3^rd^** **UNIT-IV** Digital Circuits - Counters =========================== - Asynchronous counters - Synchronous counters Asynchronous Counters --------------------- Synchronous Counters -------------------- [Digital Sequential Circuits] ========================================= Sequential Circuit **Combinational Circuits** **Sequential Circuits** ---------------------------------------- ---------------------------------------------------------- Outputs depend only on present inputs. Outputs depend on both present inputs and present state. Feedback path is not present. Feedback path is present. Memory elements are not required. Memory elements are required. Clock signal is not required. Clock signal is required. Easy to design. Difficult to design. Types of Sequential Circuits ---------------------------- - Asynchronous sequential circuits - Synchronous sequential circuits ### Asynchronous sequential circuits ### Synchronous sequential circuits Digital Circuits - Counters =========================== - Asynchronous counters - Synchronous counters Asynchronous Counters --------------------- - Asynchronous Binary up counter - Asynchronous Binary down counter ### Asynchronous Binary Up Counter  **No of negative edge of Clock** **Q~0~** LSB **Q~1~** **Q~2~** MSB ---------------------------------- -------------- ---------- -------------- 0 0 0 0 1 1 0 0 2 0 1 0 3 1 1 0 4 0 0 1 5 1 0 1 6 0 1 1 7 1 1 1 ### Asynchronous Binary Down Counter Asynchronous Binary Down Counter **No of negative edge of Clock** **Q~0~**LSB **Q~1~** **Q~2~**MSB ---------------------------------- ------------- ---------- ------------- 0 0 0 0 1 1 1 1 2 0 1 1 3 1 0 1 4 0 0 1 5 1 1 0 6 0 1 0 7 1 0 0 Synchronous Counters -------------------- - Synchronous Binary up counter - Synchronous Binary down counter ### Synchronous Binary up Counter  ### Synchronous Binary Down Counter Synchronous Binary Down Counter - Asynchronous or ripple counters. - Synchronous counters. Asynchronous or ripple counters ------------------------------- ### Logical Diagram  ### Operation **S.N.** **Condition** **Operation** ---------- ------------------------------------------------------ ------------------------- 1 **Initially let both the FFs be in the reset state** Q~B~Q~A~ = 00 initially 2 **After 1st negative clock edge** 3 **After 2nd negative clock edge** 4 **After 3rd negative clock edge** 5 **After 4th negative clock edge** ### Truth Table Synchronous counters -------------------- ### 2-bit Synchronous up counter ### Logical Diagram C:\\Users\\sai\\Desktop\\previous paper\\Digram\\synchronous ripple\_counter\_diagram.jpg ### Operation **S.N.** **Condition** **Operation** ---------- ------------------------------------------------------ -------------------------- 1 **Initially let both the FFs be in the reset state** Q~B~Q~A~ = 00 initially. 2 **After 1st negative clock edge** 3 **After 2nd negative clock edge** 4 **After 3rd negative clock edge** 5 **After 4th negative clock edge** Classification of counters -------------------------- - Up counters - Down counters - Up/Down counters UP/DOWN Counter --------------- - Type of up/down counters - UP/DOWN ripple counters - UP/DOWN synchronous counter UP/DOWN Ripple Counters ----------------------- - - ### Example - - - - - - ### Block Diagram  ### Truth Table C:\\Users\\sai\\Desktop\\previous paper\\Digram\\updown\_counter\_truthtable.jpg ### Operation **S.N.** **Condition** **Operation** ---------- --------------------------------------------- --------------- 1 **Case 1 − With M = 0 (Up counting mode)** 2 **Case 2: With M = 1 (Down counting mode)** Modulus Counter (MOD-N Counter) ------------------------------- ### Type of modulus - 2-bit up or down (MOD-4) - 3-bit up or down (MOD-8) - 4-bit up or down (MOD-16) Application of counters ----------------------- - Frequency counters - Digital clock - Time measurement - A to D converter - Frequency divider circuits - Digital triangular wave generator.