Light-weight on-chip signal monitor with integrated memory management and data collection
View Patent ↗Embodiments of a device and method to automatically acquire signal quality metrics in a digital communication system are disclosed. The device may include acquisition means to sample the likelihood of a digital communication signal passing through a grid of time and amplitude regions, and storage means by which such likelihood measurements may be accumulated in a computer memory array for analysis. A state machine may execute a method that controls both the acquisition means and the storage means, requiring minimal intervention from supervisory systems.
1. An on-chip signal monitor comprising:
a clock and data recovery (CDR) unit that provides a reference clock signal;
a state machine that includes a sequencing logic, the sequencing logic configured to set a sample gate signal to a first level to initiate each sample acquisition, the sequencing logic configured to trigger an update of at least one of a digitized time value or a digitized amplitude value;
a trigger flip flop that connects to the CDR unit to receive the reference clock signal and the sequencing logic to receive the sample gate signal, the trigger flip flop configured to pass a rising edge of the reference clock signal to an input of a programmable delay chain responsive to the sample gate signal being set to the first level;
the programmable delay chain that receives the digitized time value and outputs a delayed rising edge to a sample capture unit at a time slice window determined by the digitized time value;
the sample capture unit that, responsive to the delayed rising edge, captures a sample from an input signal within the time slice window and an amplitude slice window determined by the digitized amplitude value;
an address generator that uses the digitized time value and the digitized amplitude value to form an address of an accumulator register located in a memory; and
a load-increment-store logic that fetches a value of the accumulator register from the address of the memory, increments the value by 1, and stores the incremented value in the address.
2. The on-chip signal monitor of claim 1 , wherein:
an amplitude range of the input signal is discretized into N amplitude slice windows represented by N 1/2 bits;
a time range of the input signal across a bit interval is discretized into M time slice windows represented by M 1/2 bits; and
the memory includes N×M accumulator registers, wherein a corresponding accumulator register stores a value that represents a number of samples that fall within a corresponding amplitude slice window and a corresponding time slice window associated with the corresponding accumulator register.
3. The on-chip signal monitor of claim 1 , further comprising a leakage system that implements leakage on values of accumulator registers located in the memory.
4. The on-chip signal monitor of claim 1 , wherein the programmable delay chain includes:
a first delay unit that adjusts a relative phase of the reference clock signal; and
a second delay unit that is controlled by the sequencing logic through the digitized time value.
5. The on-chip signal monitor of claim 1 , further comprising a counter that records at least one of the digitized time value or the digitized amplitude value, wherein the sequencing logic triggers the counter to update the at least one of the digitized time value or the digitized amplitude value.
6. An on-chip signal monitor comprising:
a clock and data recovery (CDR) unit that provides a reference clock signal;
a state machine that includes a sequencing logic, the sequencing logic configured to set a sample gate signal to a first level to initiate each sample acquisition, the sequencing logic configured to trigger an update of a digitized time value;
a trigger flip flop that connects to the CDR unit to receive the reference clock signal and the sequencing logic to receive the sample gate signal, the trigger flip flop configured to pass a rising edge of the reference clock signal to an input of a programmable delay chain responsive to the sample gate signal being set to the first level;
the programmable delay chain that receives the digitized time value and outputs a delayed rising edge to a sample-and-hold circuit at a time slice window determined by the digitized time value;
a sample capture unit that includes:
the sample-and-hold circuit that captures and integrates an input signal over the time slice window to output an average voltage of the input signal responsive to the delayed rising edge; and
an analog-to-digital converter (ADC) that receives the average voltage of the input signal at the time slice window and digitizes the average voltage of the input signal to a digitized amplitude value;
an address generator that uses the digitized time value and the digitized amplitude value to form an address of an accumulator register located in a memory; and
a load-increment-store logic that fetches a value of the accumulator register from the address of the memory, increments the value by 1, and stores the incremented value in the address.
7. The on-chip signal monitor of claim 6 , wherein:
an amplitude range of the input signal is discretized into N amplitude slice windows represented by N 1/2 bits;
a time range of the input signal across a bit interval is discretized into M time slice windows represented by M 1/2 bits; and
the memory includes N×M accumulator registers, wherein a corresponding accumulator register stores a value that represents a number of samples that fall within a corresponding amplitude slice window and a corresponding time slice window associated with the corresponding accumulator register.
8. The on-chip signal monitor of claim 6 , further comprising a leakage system that implements leakage on values of accumulator registers located in the memory.
9. The on-chip signal monitor of claim 6 , wherein the programmable delay chain includes:
a first delay unit that adjusts a relative phase of the reference clock signal; and
a second delay unit that is controlled by the sequencing logic through the digitized time value.
10. The on-chip signal monitor of claim 6 , further comprising a counter that records the digitized time value, wherein the sequencing logic triggers the counter to update the digitized time value.
11. An on-chip signal monitor comprising:
a clock and data recovery (CDR) unit that provides a reference clock signal;
a state machine that includes a sequencing logic, the sequencing logic configured to set a sample gate signal to a first level to initiate each sample acquisition, the sequencing logic configured to trigger an update of a digitized time value and a digitized amplitude value;
a trigger flip flop that connects to the CDR unit to receive the reference clock signal and the sequencing logic to receive the sample gate signal, the trigger flip flop configured to pass a rising edge of the reference clock signal to an input of a programmable delay chain responsive to the sample gate signal being set to the first level;
the programmable delay chain that receives the digitized time value and outputs a delayed rising edge to a sample capture unit at a time slice window determined by the digitized time value;
the sample capture unit that, responsive to the delayed rising edge, captures a sample from an input signal if the sample is within the time slice window and an amplitude slice window determined by the digitized amplitude value;
an address generator that uses the digitized time value and the digitized amplitude value to form an address of an accumulator register located in a memory; and
a load-increment-store logic that fetches a value of the accumulator register from the address of the memory, increments the value by 1, and stores the incremented value in the address.
12. The on-chip signal monitor of claim 11 , wherein:
the amplitude slice window includes an upper threshold and a lower threshold, with the lower threshold equal to the digitized amplitude value;
the sample capture unit includes a lower comparator and an upper comparator, the lower comparator and the upper comparator configured to determine whether an amplitude of the input signal falls within the amplitude slice window at a time indicated by the time slice window; and
if the amplitude of the input signal falls within the amplitude slice window at the time indicated by the time slice window, the sample capture unit captures the sample within the time slice window and the amplitude slice window and outputs a sample-in-window signal with a trigger level to the load-increment-store logic.
13. The on-chip signal monitor of claim 11 , wherein:
an amplitude range of the input signal is discretized into N amplitude slice windows represented by N 1/2 bits;
a time range of the input signal across a bit interval is discretized into M time slice windows represented by M 1/2 bits; and
the memory includes N×M accumulator registers, wherein a corresponding accumulator register stores a value that represents a number of samples that fall within a corresponding amplitude slice window and a corresponding time slice window associated with the corresponding accumulator register.
14. The on-chip signal monitor of claim 11 , further comprising a leakage system that implements leakage on values of accumulator registers located in the memory.
15. The on-chip signal monitor of claim 11 , wherein the programmable delay chain includes:
a first delay unit that adjusts a relative phase of the reference clock signal; and
a second delay unit that is controlled by the sequencing logic through the digitized time value.
16. The on-chip signal monitor of claim 11 , further comprising a counter that records at least one of the digitized time value or the digitized amplitude value, wherein the sequencing logic triggers the counter to update the at least one of the digitized time value or the digitized amplitude value.
17. A method of acquiring samples using an automatic signal monitor, the method comprising:
setting a sample gate signal to a first level to initiate sample acquisition;
capturing an input signal over a time slice window to output an average voltage of the input signal in the time slice window, wherein the time slice window is determined by a digitized time value stored in a counter;
digitizing the average voltage of the input signal to a digitized amplitude value;
forming an address of an accumulator register based on the digitized time value and the digitized amplitude value;
fetching a value stored in the accumulator register using the address;
incrementing the value by 1; and
storing the value in the accumulator register.
18. The method of claim 17 , further comprising:
configuring a starting time slice window and an ending time slice window for a frame of samples; and
initializing the time slice window with the starting time slice window.
19. The method of claim 18 , further comprising:
determining whether the time slice window reaches the ending time slice window; and
if the time slice window does not reach the ending time slice window:
triggering an update of the digitized time value stored in the counter to determine a next time slice window;
capturing the input signal over the next time slice window to output a second average voltage of the input signal in the next time slice window;
digitizing the second average voltage of the input signal to a second digitized amplitude value;
forming a second address of a second accumulator register based on the updated digitized time value and the second digitized amplitude value;
fetching a second value stored in the second accumulator register using the second address;
incrementing the second value by 1; and
storing the second value in the second accumulator register.
20. The method of claim 19 , further comprising, if the time slice window reaches the ending time slice window:
setting a maskable interrupt flag to indicate acquisition of the frame of samples; and
incrementing a frame counter value by 1.
21. The method of claim 17 , further comprising applying leakage to values stored in accumulator registers.
22. A method of acquiring samples using an automatic signal monitor, the method comprising:
setting a sample gate signal to a first level to initiate sample acquisition;
capturing a sample within a time slice window determined by a digitized time value and an amplitude slice window determined by a digitized amplitude value, wherein the digitized time value and the digitized amplitude value are stored in a counter;
generating a sample-in-window signal with a trigger level to trigger an update of an accumulator register determined by the digitized time value and the digitized amplitude value;
forming an address of the accumulator register based on the digitized time value and the digitized amplitude value;
fetching a value stored in the accumulator register using the address;
incrementing the value by 1; and
storing the value in the accumulator register.
23. The method of claim 22 , further comprising:
configuring a starting time slice window and an ending time slice window for a frame of samples;
configuring a starting amplitude slice window and an ending amplitude slice window for the frame of samples;
initializing the time slice window with the starting time slice window; and
initializing the amplitude slice window with the starting amplitude slice window.
24. The method of claim 23 , further comprising:
determining whether the amplitude slice window reaches the ending amplitude slice window;
if the amplitude slice window does not reach the ending amplitude slice window:
triggering an update of the digitized amplitude value stored in the counter to determine a next amplitude slice window;
capturing a second sample within the time slice window and the next amplitude slice window;
forming a second address of a second accumulator register based on the digitized time value and the second digitized amplitude value;
fetching a second value stored in the second accumulator register using the second address;
incrementing the second value by 1; and
storing the second value in the second accumulator register; or
if the amplitude slice window reaches the ending amplitude slice window:
triggering an update of the digitized time value stored in the counter to determine a next time slice window; and
capturing samples associated with the next time slice window for the frame of samples.
25. The method of claim 24 , further comprising:
determining whether the time slice window reaches the ending time slice window;
if the time slice window does not reach the ending time slice window:
triggering an update of the time slice window; and
continuing to capture samples associated with the updated time slice window for the frame of samples; or
if the time slice window reaches the ending time slice window:
setting a maskable interrupt flag to indicate acquisition of the frame of samples; and
incrementing a frame counter value by 1.