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Review and Lab Prep

Review and Lab Prep. hotmail account on mailing list doesn’t work. Memory Architecture Review. Show the memory after execution from reset. indirect. direct. (sfr). xFF. xFE. 27H. A5H. Acc. MOV A,@R1;. MOV R1,A;. x80. MOV A,#FEH;. MOV 64H,A;. 20H. MOV A, FEH;. JMP 20H;. 0.

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Review and Lab Prep

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  1. Review and Lab Prep • hotmail account on mailing list doesn’t work CSE466 Autumn ‘00- 1

  2. Memory Architecture Review Show the memory after execution from reset indirect direct (sfr) xFF xFE 27H A5H Acc MOV A,@R1; MOV R1,A; x80 MOV A,#FEH; MOV 64H,A; 20H MOV A, FEH; JMP 20H; 0 CSE466 Autumn ‘00- 2

  3. Basic RC review Vo = Vi(1-e (-t/RC) ) so Vo/Vi = 4/5=.8 = (1-e (-t/RC) ) t = -RCln(1 - .8) = 49mSec 8051 + 3.2u RST 10K - what is the voltage across the cap after button release? ~4V Tr CSE466 Autumn ‘00- 3

  4. Careful w/ Coils (motors, valves, etc) • Steady state on current: Vcc/R • Vds ~ 0 (Rds ~ 4mOhm) • But, when we try to turn off the • Mosfet quickly, what happens? • Rds goes up quickly, but Ids drops slowly) • If Rds becomes 1K, then Vds becomes 100V • And instantaneous power becomes 10W 5V Current limiter R = 50Ohms I =0 .1A Coil (L) 8051 MOSFET Switch Vds CSE466 Autumn ‘00- 4

  5. could be any power device Saturation Mode Amp • Use a current amplifier (PNP Transistor) • Ice <=Ib (assume =100) • Assume Vbe = 0.7V when “on” • Assume Vce = 1V when “on” • Assume tone1 = 0V • Pick Rc to protect the speaker • Pick Rb to protect the processorwhile turning on the transistor 5V 8ohms Ib 8051 e tone1 b <Ib c Rb Is = ((.2/8)^.5)/3 = ~50mA Rc: 5 – (50mA*8) – Vce – (50mA * Rc) = 0so: Rc = (5 – 1 – 0.4)/.05 = 72ohms Rb: Vb/1mA = [5 – (8*.05) - .7]/1mA = 3.9K! Rc CSE466 Autumn ‘00- 5

  6. Last Year’s Model 5V 8ohms 8051 Rb tone1 tone2 tone3 Rc CSE466 Autumn ‘00- 6

  7. This Year’s Model • Digital to Analog Converter Computer Speaker 8051 8 SW? DAC AMP (V to I) Voltage signal Speaker cares about current, not voltage How can we generate two simultaneous tones of 500Hz and 1KHz using only 1 timer interrupt? CSE466 Autumn ‘00- 7

  8. Sine Wave Program (in psuedo-C) const unsigned byte sine[256] = { }; interrupt routine (25.6KHz): P0 = sine[i]; i++; returnHow do I get two tones with one interrupt (constant sample rate) ? rom CSE466 Autumn ‘00- 8

  9. Digital to Analog Converter each bit pumps more current into Rfbin different amounts depending on position 5V 20K out1 Effective network is 10K DB[7:0] = 10000000 out = DB[7:0] = 10000001 out = MSB CSE466 Autumn ‘00- 9

  10. Digital-to-Analog Converter Vref AMP input out1 CS 8051 DAC \write Rfb data port0 gnd CSE466 Autumn ‘00- 10

  11. Sampling • Add sampled sine waves to get multiple tones two frequencies with same rate. How fast can you go? CSE466 Autumn ‘00- 11

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