More digital circuits
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More Digital circuits. Ripple Counter. The most common counter The problem is that, because more than one output is changing at once, the signal is glichy To avoid this problem, use Gray or Johnson code. Johnson Counter. The Johnson counter is type of shift counter

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More Digital circuits

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More digital circuits

More Digital circuits


Ripple counter

Ripple Counter

  • The most common counter

  • The problem is that, because more than one output is changing at once, the signal is glichy

  • To avoid this problem, use Gray or Johnson code


Johnson counter

Johnson Counter

  • The Johnson counter is type of shift counter

  • Put an inverted MSB back to LSB

  • Glitch output free


Johnson counter with error recovery

Johnson Counter with error recovery


Linear feedback shift registers

Linear Feedback Shift Registers

  • A small number of taps are recycled

  • An LFSR can operate at high speed compared to a binary counter because the feedback logic is very simple

  • Reduce clock noise


Many to one lfsr

Many-to-One LFSR


Many to one lfsr1

Many-to-One LFSR


Maximal length lfsr

Maximal length LFSR

  • With maximal length logic (taps selected to givethe maximal count),a small number of register can create sequence up to 2n-1


Divide by n lfsr counter

Divide by N LFSR Counter

  • An example of the use of a LFSR

  • A terminal count is provided as an input to be compared to


Divide by n lfsr counter1

Divide by N LFSR Counter

  • Test fixture


4 bit lfsr one to many code

4-Bit LFSR One-to-Many Code

  • One-to-Many variant splits the XOR into 2-input gates and distributes them throughout the register array


Cyclic redundancy checksums

Cyclic Redundancy Checksums

  • Error detection

  • The data packet is looked at as a huge binary number

  • A polynomial divide this number in GF

  • Reminder is checksum


Cyclic redundancy checksums1

Cyclic Redundancy Checksums


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ROM

  • ROM stands for Read-Only Memory

  • This memory is initialized when the FPGA is configuredand cannot be changedafter configuration


Rom version of lfsr

ROM Version of LFSR

  • We can implement four-bit LFSR counter with a ROM


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RAM

  • RAM stands for Random Access Memory

  • A RAM is an array of cells, addressable in groups N element wide and M elements deep


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RAM


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RAM

  • Unless the FPGA support embedded RAM blocks, it will consume a huge amount of logic


Fpga with embedded ram

FPGA with embedded RAM


256x8 ram implemented in the 4000xl device family

256x8 RAM Implemented in the 4000XL Device Family


Dual port ram

Dual port RAM


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  • Jovan Popovic [email protected]

  • Milos Milovanovic [email protected]

  • Veljko Milutinovic [email protected]

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