【正文】 value before entering the algorithm. Then calculate the disparity for the rightmost 4 bits keeping in mind the disparity value determined after analyzing the previous 6 bits. The disparity for both the 6bit and the 4bit blocks should be calculated as follows: 61 12/4/2020 Differential Signaling 下載 8b/10b Running Disparity Calculation Method ? Method: If of 1’s 0’s Disparity = Positive (1) Else if of 0’s 1’s Disparity = Negative (0) Else if 6bit = 000111 Then Disparity = Positive (1) Else if 6bit = 111000 Then Disparity = Negative (0) Else if 4bit = 0011 Then Disparity = Positive (1) Else if 4bit = 1100 Then Disparity = Negative (0) Else Disparity = Disparity (if none of the above, then the disparity value doesn’t change) Note: Assuming a encoding, more 1’s across the entire 10b code yields positive disparity, more 0’s yields negative disparity, and even ’s of 1’s and 0’s yields neutral disparity (. disparity is the same as it was before). 62 12/4/2020 Differential Signaling 下載 8b/10b Disparity amp。 o = b/2。 e = c Line 1 Line 2 Reference 8 12/4/2020 Differential Signaling 下載 Propagation Terms to Consider ?Differential mode propagation ?Common mode propagation ?Single ended mode (uncoupled) propagation This is when the other line is not driven but terminated to absorbed reflections. ?Transmission line matrixes will reflect these modes. 9 12/4/2020 Differential Signaling 下載 Differential Microstrip Example Z0 Zs e??S s e 1 . 9 9 2nsft?S s e L 1 1 C 1 1???Zs e 3 9 . 7 4 4 ??Zs eL 1 1C 1 1??Sc 1 . 9 9 6nsft?Sc L 1 1 L 2 1?( ) C 1 1 C 2 1?( )???Zc o m m 4 7 . 4 2 2 ??Zc o m mL 1 1 L 2 1?C 1 1 C 2 1???Sd 1 . 9 2 4nsft?Sd L 1 1 L 2 1?( ) C 1 1 C 2 1?( )???Zd i f f 6 6 . 1 8 5 ??Zd i f f 2L 1 1 L 2 1?C 1 1 C 2 1???i n d u c ta n c e an d c ap ac i ta n c e m at r i x e sC 1 1C 1 2?C 2 1?C 2 2??????L 1 1L 1 2L 2 1L 2 2??????T r an s m i s s i o n l i n eC 2 2 C 1 1??C 1 2 C 2 1??C 2 1 6 . 6 9 0 0 0 0 101 3?f a r a din??C 1 1 4 . 1 7 7 0 0 0 101 2?f a r a din??L 2 2 L 1 1??L 1 2 L 2 1??L 2 1 1 . 2 9 1 0 0 0 109?h e n r yin??L 1 1 6 . 5 9 8 0 0 0 109?h e n r yin??SE: single ended = uncoupled 10 12/4/2020 Differential Signaling 下載 Differential Impedance ?Coupling between lines in a pair always decreases differential impedance ?Differential impedance is always less that 2 times the uncoupled impedance ?Differential impedance of uncoupled lines is 2 times the uncoupled impedance. 11 12/4/2020 Differential Signaling 下載 Propagation Velocities ?For TEM structures, (striplines) Differential mode, Common Mode, and single ended velocities are the same ?For Non TEM and QuasiTEM structures (microstrip) Differential mode, Common Mode, and single ended velocities and impedances are not the same. Common mode can be converted to differential mode at a receiver and result in a differential signal disturbance. 12 12/4/2020 Differential Signaling 下載 Example of Common Mode ? Line 1 and line 2 have the same DC offset. This is DC mon mode. It can be defined as an average DC for time duration of many UI cycles value as well. ? Line1 and line 2 have the same AC offset ? This is AC mon mode ? AC mon mode also result from time differences (skew) between signal on line 1 and line 2. This can result in AC mon mode and differential signal loss. ? The following slide will be used to clarify the above 13 12/4/2020 Differential Signaling 下載 Differential Signaling Basics ? For long channels, at GHz frequencies, signal tend look like sine waves. ? The artificial offset mon to line 1 and 2 has an average of 1 and varies around that average by +/ in a period manor. V o l t a g e s a a n d b a re re s p e c t i v e o f s i g n a l s o n l i n e s 1 a n d 2W e w i l l u s e a 1 G H z s i n e w a v e f o r t h e s i g n a l a n d o f f s e t d e f i n e d b e l o wo ff s e t i .9 m o dt ins1f ns????????.2???? ra m p w a v e c e n t e re d a ro u n d 1a i s i n 2 ?? f? t i?? ? o ff s e t i??? b i s i n 2 ?? f? t i?? ?? o ff s e t i???14 12/4/2020 Differential Signaling 下載 Individual signals Pl o t i n d i v i d u a l l i n e v o l t a g e s a n d o f f s e t v o l t a g e0 0. 83 1. 67 2. 5 3. 33 4. 17 510. 330. 3311. 672. 333aibioff setitins? Devices need to have enough mon mode dynamic voltage range to receive or transmit the waveforms. In this case the signals swing between and . ? The sine wave amplitude is 1 and peak to peak is 2. ? Signal a and b is what would be observed with 2 oscilloscope probes 15 12/4/2020 Differential Signaling 下載 Differential Mode Signal 0 0. 83 1. 67 2. 5 3. 33 4. 17 521012a b?tnsPl o t D i f f e re n t i a l v o l t a g e? The differential amplitude is 2 and peak to peak is 4 which is 2 times the individual signal peak to peak amplitude. ? Notice the distortions are gone. 16 12/4/2020 Differential Signaling 下載 Common Mode Signal ? The DC mon mode signal is 1 ? The AC mon mode signal is .2 v peak to peak Some may specifications may call this v peak from the DC average ? We will add this mon mode to the signals “a” and “b” Pl o t c o m m o n m o d e v o l t a g e0 1 2 3 4 50. 80. 911. 1aibi?2tins17 12/4/2020 Differential Signaling 下載 Add 150 ps skew to signal b Pl o t i n d i v i d u a l l i n e v o l t a g e s a n d o f f s e t v o l t a g e0 0. 83 1. 67 2. 5 3. 33 4. 17 510. 330. 3311. 672. 333aibioff setit