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ee120a Lecture 16 Suppl - Binary Arithmetic, ADC-DAC Signal Encoding

Ee120a Lecture 16 Suppl - Binary Arithmetic, ADC-DAC Signal Encoding

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ee120a Logic Design ee128 Data Acquisition, Interfacing & Control Department of Electrical Engineering University of California – Riverside Instructor: Roman Chomko EE 120A Lecture 16, Supplement Winter 2009 EE128 Lecture 2 Fall 2008 ee120a Lecture 16, Supplement ee128 Lecture # 2 BINARY ARITHMETIC, ADC/DAC SIGNAL ENCODING Lecture Plan 1. ENCODING OF ADC/DAC SIGNALS 1 2. BINARY ARITHMETIC 10

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EE128 LECTURE 2 Lecture 16, Supplement EE 120A Winter 2009 2 EE128 LECTURE 02 BINARY ARITHMETIC, ADC/DAC SIGNAL ENCODING 1. ENCODING OF ADC/DAC SIGNALS 1.1 DATA ACQUISITION PROBLEM AND DIGITAL SIGNALS In the continuous control problem shown in the Example 1 of Lecture 01 and reproduced in the Figure 1 below the sequence TEMPERATURE SENSOR barb2right A/D barb2right COMPUTER represents a typical DATA ACQUISITION SYSTEM (DAS) . A generic Data Acquisition Problem can be stated as For a signal processor (computer), how are the various errors identified and quantified so that for a given value of N (number of bits) the effect of those errors is minimized? Figure 1. Example 1 of Lecture 1 Many types, sizes, and definitions of binary digit strings may be processed by a computer in a single application. The smallest unit a digital computer works with is a bit (‘0’ or ‘1’). The other types of strings are classified according to the Table 1 . MSB LSB 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 bit nibble nibble nibble nibble byte (high-order byte) byte (low-order byte) word Table 1. Bit configuration within a 16-bit word
EE128 LECTURE 2 Lecture 16, Supplement EE 120A Winter 2009 3 NOTE : in a Digital Processing Unit the bit string with which the Unit works is called a word . However, this term typically (but not always) is used to refer to a 16-bit (2-byte) configuration. Very often we will need to refer to words of other bit sizes , for example in data lines of N-bit word size. Before the ADC (analog-to-digital) conversion can be performed the signal (typically, the voltage) must be properly conditioned: SIGNAL CONDITIONING The processing of a waveform or pattern of a signal to ensure a compatibility with a device Than, the function of an ADC block is to convert a band-limited * time-signal y(t) into a sequence of binary words, in our case y(t)= Temperature(t) . Each word corresponds to the value of Y(t) at a particular time nT denoted as Y(nT) ( ˆ T in the Figure) where T is the time interval between samples and n is the sample number from some starting time t= t 0 . Thus the words would correspond to values Y (0), Y ( T ), Y (2 T ), … taken at times t , t 0 + T , t 0 + 2 T , … and so on. Each Y is a binary word of N bits. Figure 2. ADC (analog-to-digtal) analog signal digitization 1.2 BINARY CODING SCHEMES The process of constructing a word is called CODING , and the way the bits are arranged within the word is the CODING SCHEME .

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Ee120a Lecture 16 Suppl - Binary Arithmetic, ADC-DAC Signal Encoding

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