Analog to Digital Conversion：.ppt

Chap 0 * Commercially available monolithic ADCs Chap 0 * Commercially available hybrid ADCs Chap 0 * A low cost DAS for the IBM PC Multi-channel system Less than $100 ADC0816 from National Semiconductor Constant, repetitive rate 1000 samples/s Generating clock For starting ADC conversion For causing interrupt Make a pulse stream from TCLK with short pulses of duration = ? x BCLK/4 TCLK from 8253 Timer/Counter Wide pulse Chap 0 * ADC circuit for PC prototype board SCSLCT (Start Conversion SeLeCT) : Latched trough port 30CH SCSLCT = H Selection of 30AH (/E10) start conversion SCSLCT = L TCLK’ start conversion INTSLCT (INTerrupt SeLeCT) : Latched trough port 30CH INTSLCT = H EOC cause IRQ2 INTSLCT = L No Interrupt CPU read Status register (Port 309H) to check EOC Chap 0 * Status Register For polling TCLK and EOC signal Port 309H (/E9) Polling of EOC results in a low level after the data from ADC have been read Chap 0 * Throughput rate calculation 4.77MHz / 8 = 596KHz Chap 0 * Accuracy Calculation Better than 1% accuracy is ensured Actual accuracy with smooth input signal at room temperature will be better than 0.5% Chap 0 * Basic Program for Controlling ADC Sampling rate 200 samples/s Because OUT and IN instruction in Basic takes 5ms Chap 0 * C Programming for Controlling ADC Sampling from ADC channel 1 at 5ms interval and sending each sampled data point to the DAC Chap 0 * Homework #5-2 Prototype board? ?? ?? ???? ?? C program? ???? ??? ???? ?? ?? Outp(CNTRL,5)? ???? ??? ?? ?? ??? ????? ?…. * Analog to Digital Conversion ADC Essentials A/D Conversion Techniques Interfacing the ADC to the IBM PC DAS (Data Acquisition Systems) How to select and use an ADC A low cost DAS for the IBM PC Chap 0 * Why ADC ? Digital Signal Processing is more popular Easy to implement, modify, … Low cost Data from real world are typically Analog Needs conversion system from raw measurements to digital data Consists of Amplifier, Filters Sample