Data Streams 03/04/2008 Lecture 14 1 Winter 2012 UCSD: Physics 121; 2012 2 1st data packet 2nd data packet Winter 2012 UCSD: Physics 121; 2012 3 Transmitter 55573 sends an “A” Transmitter 55573 sends a “B” first packet second packet first packet second packet Winter 2012 UCSD: Physics 121; 2012 4 Differences are minor, showing up only near beginning & end We will represent “high” states (light on) as 1’s, and lows (off) as 0’s Notice standard widths: choices are single- or double-width (both for the zeros and the ones)Data Streams 03/04/2008 Lecture 14 2 Winter 2012 UCSD: Physics 121; 2012 5 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Sequence starts out: 01101001001101001001001001… Notice the 01 delimiters: 01101001001101001001001001… This gives the signal its choppy appearance (never see 3 1’s or 0’s in a row) Actual data appears between delimiters: 1’s look fat, 0’s look skinny Resulting bit-sequence for A signal (both packets) is: button code transmitter ID (normal and inverted) checksum end delimiter Winter 2012 UCSD: Physics 121; 2012 6 B A C D E 1001 → 001 → 1 1010 → 010 → 2 1011 → 011 → 3 1100 → 100 → 4 1101 → 101 → 5 first bit always 1 << 1110 → 110 → 6 Winter 2012 UCSD: Physics 121; 2012 7 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 2 4 8 32768 16384 8192 4096 2048 1024 512 256 128 64 32 16 Winter 2012 UCSD: Physics 121; 2012 8 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 button code transmitter ID (normal first-packet version) checksum Break data into chunks of 8 bits (bytes) and add up: 1001 00000000 11011001 00010101 11110111 Checksums provide a “sanity check” on the data integrityData Streams 03/04/2008 Lecture 14 3 Winter 2012 UCSD: Physics 121; 2012 9 1 0 1 0 1 0 0 0 0 1 1 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1 1 0 1 1 1 0 1 0 1 0 1 0 0 0 1 0 1 1 1 1 0 1 1 0 E-button on H-ITT (first of two packets): 1st data packet 2nd data packet H-ITT bursts serial bursts Winter 2012 UCSD: Physics 121; 2012 10 data packet data packet data packet Winter 2012 UCSD: Physics 121; 2012 11 POWER VOL + VOL - 1 2 3 4 5 6 7 remote ID? data 101001000 011001000 111001000 000000000 100000000 010000000 100000 010000 110001000 001001000 Winter 2012 UCSD: Physics 121; 2012 12 1 1 1 1 1 0 0 1 1 0 1 0 0 1 0 0 0 data part ID partData Streams 03/04/2008 Lecture 14 4 Winter 2012 UCSD: Physics 121; 2012 13 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 1 1 0 0 0 0 1 1 1 1 1 0 0 0 0 zeros ones mixed traditional Winter 2012 UCSD: Physics 121; 2012 14 track 3 track 1 track 2 data direction Winter 2012 UCSD: Physics 121; 2012 15 --Data Bits-- Parity! b1 b2 b3 b4 b5 Character Function! 0 0 0 0 1 0 (0H) Data! 1 0 0 0 0 1 (1H) "! 0 1 0 0 0 2 (2H) "! 1 1 0 0 1 3 (3H) "! 0 0 1 0 0 4 (4H) "! 1 0 1 0 1 5 (5H) "! 0 1 1 0 1 6 (6H) "! 1 1 1 0 0 7 (7H) "! 0 0 0 1 0 8 (8H) "! 1 0 0 1 1 9 (9H) "! 0 1 0 1 1 : (AH) Control! 1 1 0 1 0 ; (BH) Start Sentinel! 0 0 1 1 1 < (CH) Control! 1 0 1 1 0 = (DH) Field Separator! 0 1 1 1 0 > (EH) Control! 1 1 1 1 1 ? (FH) End Sentinel!Winter 2012 UCSD: Physics 121; 2012 16Data Streams 03/04/2008 Lecture 14 5 Winter 2012 UCSD: Physics 121; 2012 17 Winter 2012 UCSD: Physics 121; 2012 18 R S Q Q D CLK Winter 2012 UCSD: Physics 121; 2012 19 Winter 2012 UCSD: Physics 121; 2012 20Data Streams 03/04/2008 Lecture 14 6 Winter 2012 UCSD: Physics 121; 2012 21 Winter 2012 UCSD: Physics 121; 2012 22 Winter 2012 UCSD: Physics 121; 2012