14_data_stream

Winter 2008 lecture 14 data packet serial bursts h itt

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Unformatted text preview: ote uses a different scheme: 100000 2 111001000 remote ID? Winter 2008 Lecture 14 data packet serial bursts H-ITT bursts 1st data packet • 100010001000100010001010100010001010001010… ID part data part 1 1 1 1 1 00 1 1 0 1 00 1 000 – in data part, least significant bit (LSB) is first – so the number part of “5” is 101001000 1 010 – least significant digit is first, so reverse order for more familiar form: 0101 = 5 data 11 Winter 2008 12 3 Data Streams 03/04/2008 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 Magstripe Idea • On magnetic stripe, N-S junctions eat their own magnetic flux lines, but N-N or S-S present external flux lines of opposite direction – pattern of N-N and S-S creates + and transitions – zero represented by long period – one represented by short period – zeros look fat; zeros thin (sign irrelevant) – two streams are produced from this: Magstripe Geometry zeros 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 0 0 1 1 0 1 0 1 1 0 0 1 1 0 1 0 1 ones data direction track 3 track 2 mixed traditional • a data stream • a clock – data valid when clock high Winter 2008 13 track 1 • There are up to three tracks of data – Tracks 1 and 3 typically higher-density (7-bit) alpha-numeric data – Track 2 typically lower-density (5-bit) numeric data – Track 2 used on almost every card; track 1 often, track 3 seldom Winter 2008 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 Track 2 Character Code - -Data Bits-b1 b2 b3 b4 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 Winter 2008 Lecture 14 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 Parity b5 Character 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 0 1 2 3 4 5 6 7 8 9 : ; < = > ? (0H) (1H) (2H) (3H) (4H) (5H) (6H) (7H) (8H) (9H) (AH) (BH) (CH) (DH) (EH) (FH) 14 Mag-stripe Circuit Schematic Function Data " " " " " " " " " Control Start Sentinel Control Field Separator Control End Sentinel 15 Winter 2008 16 4 Data Streams 03/04/2008 UCSD: Physics 121; 2008 UCSD: Physics 121; 2008 Unfamiliar bits The D-type flip-flop • You’ve seen many of the elements in the circuit by You’ now S D Q – AND, NOR, NOT logic • New pieces are down-counter, flip-flops (and latch version thereof) • Also have a PIC microcontroller and an RS-232 level converter Winter 2008 17 CLK Q R • Rules: – whatever logic level sits at D input, it gets transferred to Q (and inverse logic to Q-bar)...
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This note was uploaded on 01/30/2014 for the course PHYS 121 taught by Professor Staff during the Winter '08 term at UCSD.

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