Adaptive level binary logic
View Patent ↗A digital logic interface circuit makes use of a logic signal representative of a logic signaling level definition, to determine the logic swing amplitude of signals from a given source adopting the same logic signaling level definition. The digital logic interface circuit generates a threshold level from the logic swing amplitude thus determined, and compares digital logic input signals against the threshold level in order to discriminate different logic levels in the digital logic input signals. The comparison result is provided as digital interface output signals adopting a predetermined logic signaling level definition for use by subsequent system sections. Examples of such representative signals are the digital input logic signals themselves, clock signals or line encoded signals. Other examples can be mode control signals or NRZ signals.
1. A digital logic signal interface circuit ( 1 ) for adaptively receiving and discriminating at least one digital logic input signal ( 31 , 32 ) taking signal amplitude levels each representative of one of a plurality of different logic levels in accordance with a logic signalling definition, said digital logic signal interface circuit ( 1 ) comprising
a circuit ( 2 ) adapted to receive a digital logic representative signal ( 31 ) taking signal amplitude levels representative of said logic signalling definition, for generating a threshold signal (Vth) depending on a logic swing amplitude occurring in said digital logic representative signal ( 31 ), said threshold signal generating circuit ( 2 ) comprising an amplitude detector circuit ( 21 , 22 ) for detecting at least one signal amplitude level repetitively taken by said digital logic representative signal ( 31 ), and for providing at least one amplitude detection signal (V+, V−) which is indicative of said at least one detected signal amplitude level;
a logic level discriminator circuit ( 41 , 42 ) adapted to receive said at least one digital logic input signal ( 31 , 32 ) and said threshold signal (Vth), and adapted to provide for each of said at least one digital logic input signal a corresponding digital interface output signal ( 51 , 52 ) taking one of a plurality of predetermined signal amplitude levels indicative of a result of comparing said digital logic input signal ( 31 , 32 ) amplitude level to said threshold signal (Vth); characterized by
at least one output buffer circuit ( 4 ) adapted to receive a digital logic interface input signal ( 53 ) and to generate in accordance therewith, a digital logic output signal ( 33 ) taking signal amplitude levels each representative of one of said plurality of different logic levels;
said output buffer circuit ( 4 ) being coupled to receive said at least one amplitude detection signal (V+, V−) from said amplitude detector circuit ( 21 , 22 ) and to generate said signal amplitude levels in accordance with said at least one amplitude detection signal, such that said digital logic output signal ( 33 ) can adaptively meet said logic signalling definition of said digital logic input signal ( 31 , 33 ).
2. The digital logic signal interface circuit according to claim 1 , wherein said threshold signal generating circuit ( 2 ) comprises
a threshold generator circuit ( 2340 , 2341 ) for generating said threshold signal (Vth) depending on said at least one amplitude detection signal (V+, V−).
3. The digital logic signal interface circuit ( 1 ) according to claim 2 , wherein said amplitude detector circuit ( 21 , 22 ) comprises a peak detector circuit for extracting at least one peak amplitude level in said digital logic representative signal ( 31 ).
4. The digital logic signal interface circuit according to claim 2 , wherein said amplitude detector circuit ( 2321 , 2324 ; 2331 - 2333 ; 211 , 221 ) comprises an edge detector circuit for detecting the occurrence of edges in said digital logic representative signal, and a sampling circuit ( 2322 , 2323 ; 2338 , 2339 ; 212 , 222 ) for sampling the signal amplitude of said digital logic representative signal ( 31 ) at times controlled by said edge detector circuit.
5. The digital logic signal interface circuit ( 1 ) according to claim 4 , wherein said sampling circuit ( 2322 , 2323 , 212 , 222 ) is adapted to sample the signal amplitude of said digital logic representative signal during an extended sampling time interval, and to generate said amplitude detection signal (V+, V−) based on low pass filtering the section of said digital logic representative signal ( 31 ) taken during said extended sampling time interval.
6. The digital logic signal interface circuit ( 1 ) according to claim 5 , wherein said sampling circuit ( 2322 , 2323 , 2328 , 2325 ) is adapted to generate said amplitude detection signal based on a time average of or low pass filter operation performed on the signal amplitude of said digital logic representative signal ( 31 ) section taken during said extended sampling time interval.
7. The digital logic signal interface circuit according to claim 5 , wherein said extended sampling time interval has a duration in the order of half the data clock period of said digital logic representative signal ( 31 ).
8. The digital logic signal interface circuit according to claim 5 , wherein said extended sampling time interval extends from one edge occurring in said digital logic representative signal ( 31 ) to the next edge in said digital logic representative signal ( 31 ).
9. The digital logic signal interface circuit according to claim 4 , comprising a sampling delay circuit for delaying sampling of said digital logic representative signal ( 31 ) by a predetermined amount after the occurrence of an edge in said digital logic representative signal ( 31 ).
10. The digital logic signal interface circuit according to claim 1 wherein
said amplitude detector circuit ( 21 , 22 ) is adapted to detect a high signal amplitude level and furthermore, a low signal amplitude level taken by said digital logic representative signal ( 31 ), and to provide corresponding high amplitude and low amplitude detection signals (V+, V−), respectively; and
said threshold generator circuit ( 2 ) comprises a level averaging circuit ( 23 , 2340 , 2341 ) coupled to provide an average of said high amplitude and low amplitude detection signals as said threshold signal.
11. The digital logic signal interface circuit ( 1 ) according to claim 1 , wherein
said amplitude detector circuit is adapted to detect a high signal amplitude level taken by said digital logic representative signal, and to provide a corresponding high amplitude detection signal; and
said threshold generator circuit ( 2 ) comprises a signal level divider circuit for dividing the signal level of said high amplitude detection signal by about two, in order to provide said threshold signal.
12. The digital logic interface circuit ( 1 ) according to claim 1 , wherein said threshold signal generating circuit ( 2 ) comprises a low pass filter circuit ( 23 ) for filtering said digital logic representative signal ( 31 ) and extracting a DC component therein as said threshold signal.
13. The digital logic interface circuit ( 1 ) according to claim 12 , wherein said low pass filter circuit ( 23 ) comprises a sample and hold circuit for sampling said digital logic representative signal, an analog to digital converter for converting the samples provided by said sample and hold circuit into a digital representation, a digital filter circuit for processing the digital samples obtained from said sample and hold circuit, and a digital to analog converter for converting the digital output of said digital filter into said threshold signal (Vth).
14. The digital logic interface circuit ( 1 ) according to claim 1 , wherein said circuit ( 2 ) for generating a threshold signal is coupled with said logic level discriminator circuit ( 41 , 42 ) to receive said digital logic input signal received by said logic level discriminator circuit as said representative signal ( 31 ).
15. The digital logic interface circuit ( 1 ) according to claim 1 , wherein said circuit for providing a threshold signal (Vth) is coupled to receive a digital logic signal ( 31 ) different from said at least one digital logic input signal ( 32 ) as said digital logic representative signal.
16. The digital logic interface circuit ( 1 ) according to claim 15 , wherein said digital logic representative signal ( 31 ) is a clock signal and said at least one digital logic input signal is a data signal.
17. The digital logic interface circuit ( 1 ) according to claim 1 , wherein said logic level discriminator circuit ( 41 , 42 ) is adapted to provide said at least one digital interface output signal ( 51 , 52 ) at a first one of said predetermined signal levels when said corresponding digital logic input signal ( 31 , 32 ) has a signal level above said threshold signal level (Vth), and at a second one of said predetermined signal levels when said corresponding digital logic input signal ( 31 , 32 ) has a signal level below said threshold signal level (Vth).
18. A digital logic circuit ( 1 , 5 ) having at least one input ( 31 , 32 ) for receiving at least one digital logic input signal taking signal amplitude levels each corresponding to one of a plurality of different logic levels, and at least one output ( 33 ) for outputting at least one digital logic output signal, furthermore having a digital logic processing circuit ( 5 ) for performing logical operations on said at least one digital logic input signal, and for providing at least one logic output signal ( 53 ), said,digital logic circuit comprising a digital logic interface circuit ( 1 ) according to claim 1 , coupled between said input ( 31 , 32 ) and output ( 33 ) on the one hand and coupled on the other hand to receive from said logic processing circuit ( 5 ) said at least one digital logic interface input signal ( 53 ) and to provide to said logic processing circuit said at least one digital logic interlace output signal ( 51 , 52 ).