1 / 24

ENGR/ECE 212 21 February, 2003

ENGR/ECE 212 21 February, 2003. All slides except those with blue backgrounds are taken from John Wakerly’s Stanford EE 121, Digital Design Laboratory. Decoders. General decoder structure Typically n inputs, 2 n outputs 2-to-4, 3-to-8, 4-to-16, etc. with a few enable inputs.

quilla
Télécharger la présentation

ENGR/ECE 212 21 February, 2003

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. ENGR/ECE 21221 February, 2003 All slides except those with blue backgrounds are taken from John Wakerly’s Stanford EE 121, Digital Design Laboratory

  2. Decoders • General decoder structure • Typically n inputs, 2n outputs • 2-to-4, 3-to-8, 4-to-16, etc. • with a few enable inputs

  3. Note “x” (don’t care) notation. Binary 2-to-4 decoder

  4. MSI 2-to-4 decoder • Input buffering (less load) • NAND gates (faster)

  5. Decoder Symbol

  6. 3-to-8 decoder

  7. 74x138 3-to-8-decoder symbol

  8. Decoder cascading 4-to-16 decoder

  9. More cascading 5-to-32 decoder

  10. ABEL / PAL Version of 74x138 module Z74X138 title '74x138 Decoder PLD J. Wakerly, Stanford University‘ "Z74X138 device 'P16L8'; " Input pins A, B, C, !G2A, !G2B, G1 pin 1, 2, 3, 4, 5, 6; " Output pins !Y0, !Y1, !Y2, !Y3 pin 19, 18, 17, 16 istype 'com'; !Y4, !Y5, !Y6, !Y7 pin 15, 14, 13, 12 istype 'com'; " Constant expression ENB = G1 & G2A & G2B;

  11. ABEL decoder program (continued equations Y0 = ENB & !C & !B & !A; Y1 = ENB & !C & !B & A; Y2 = ENB & !C & B & !A; Y3 = ENB & !C & B & A; Y4 = ENB & C & !B & !A; Y5 = ENB & C & !B & A; Y6 = ENB & C & B & !A; Y7 = ENB & C & B & A; end Z74X138

  12. Decoder applications • Microprocessor memory systems • selecting different banks of memory • Microprocessor input/output systems • selecting different devices • Microprocessor instruction decoding • enabling different functional units • Memory chips • enabling different rows of memory depending on address • Lots of other applications

  13. Some decoder datasheets • 74x138 • 3-line to 8-line decoders/demultiplexers • 74x139 • Dual 2-line to 4 line decoders/demultiplexers • 74x154 • 4-to-16 line decoders/demultiplexers

  14. Decoder Encoder Encoders vs. Decoders

  15. Binary encoders

  16. Need priority in most applications

  17. 8-input priority encoder

  18. 74x148 8-input priority encoder • Active-low I/O • Enable Input • “Got Something” • Enable Output

  19. 74x148circuit

  20. Cascading priority encoders • 32-inputpriority encoder

  21. Some encoder datasheets • 74x148 • 8-line to 3-line priority encoders • 74x147 • 10-line to 4-line priority encoders

  22. Multiplexers

  23. 74x1518-input multiplexer

  24. Some multiplexer datasheets • 74x151 • 8-Input Multiplexer • 74x153 • Dual 4-Input Multiplexer • 74x157, 74x158 • Quad 2-Input Multiplexer

More Related