Data eye monitor method and apparatus

• US 8,108,738 B2
• Filed: 06/26/2007
• Issued: 01/31/2012
• Est. Priority Date: 06/26/2007
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gara, Alan G., Marcella, James A., Ohmacht, Martin
• Primary Examiner(s): CHAUDRY, MUJTABA M
• Application Number:
  US11/768,810
• Publication Number:
  US 20090006730A1
• Time in Patent Office: 1,680 Days
• Field of Search: 714/700, 711/167, 375/355
• US Class Current: 714/700
• CPC Class Codes: G06F 13/1689 Synchronisation and timing concerns synchronisation on a memory bus G06F13/4234

Abstract

An apparatus and method for providing a data eye monitor. The data eye monitor apparatus utilizes an inverter/latch string circuit and a set of latches to save the data eye for providing an infinite persistent data eye. In operation, incoming read data signals are adjusted in the first stage individually and latched to provide the read data to the requesting unit. The data is also simultaneously fed into a balanced XOR tree to combine the transitions of all incoming read data signals into a single signal. This signal is passed along a delay chain and tapped at constant intervals. The tap points are fed into latches, capturing the transitions at a delay element interval resolution. Using XORs, differences between adjacent taps and therefore transitions are detected. The eye is defined by segments that show no transitions over a series of samples. The eye size and position can be used to readjust the delay of incoming signals and/or to control environment parameters like voltage, clock speed and temperature.

Claims

1. An apparatus for tracking a data eye window of a capture device receiving a plurality of data bit signals to be captured from a memory storage device, said capture device further receiving a strobe signal for latching the plurality of data bit signals at said capture device, said apparatus comprising:

a balanced tree network comprising a plurality of inputs, each of the inputs for receiving at least one of said data bit signals input from the memory storage device in coordination with said strobe signal, the balanced tree network generating an output signal associated with said plurality of data bit signals; and

a tapped inverter chain receiving said output signal for generating a persistent data eye signal;

wherein said persistent data eye signal is used to adjust said strobe signal associated with data eye centering of said capture device;

wherein said tapped inverter chain comprises;

a serial connection of n number of inverter devices, each of the inverter devices providing a fixed delay time interval, and each of the inverter devices providing a respective output signal;

n number of latch devices, each latch device being associated with a respective inverter device for latching a respective output signal from each of the inverter devices; and

n−

1 number of comparison devices, each comparison device receiving a respective latched output signal from one of the latch devices, each comparison device receiving a latched output signal of a next latch device, and each comparison device determining a presence or an absence of a transition at a delay element interval resolution;

wherein n is an integer greater than 1.

2. The apparatus as claimed in claim 1, wherein said balanced tree network is an XOR network, said output signal comprising a parity signal associated with said plurality of data bit signals in a memory storage transfer cycle.

3. The apparatus as claimed in claim 1, further comprising:

signal adjust means for first receiving said plurality of data bit signals and aligning one or more of said plurality of data bit signals according to a slowest received data bit signal prior to input to said balanced tree network.

4. The apparatus as claimed in claim 1, further comprising:

means associated with each respective comparison device for latching an output of each respective comparison device, said persistent data eye signal represented as a series of latched data bits output from said tapped inverter chain.

5. The apparatus as claimed in claim 1, wherein each tap along said tapped inverter chain represents a time accumulation for building said persistent data eye signal, a location of a transition present along said tapped inverter chain indicating an edge of said data eye window.

6. The apparatus as claimed in claim 5, wherein movement of the location of the transition along said tapped inverter chain indicates a time shift relative to a centered data eye position, said apparatus further comprising means for adjusting said strobe signal in accordance with said time shift.

7. The apparatus as claimed in claim 4, wherein said means associated with each respective comparison device for latching an output of each respective comparison device further comprises a register device accessible by a programmed processor device adapted for accessing said latched data bits output of said persistent data eye signal and initiating adjustment of said strobe signal.

8. The apparatus as claimed in claim 5, wherein said persistent data eye signal is updated every valid data transfer cycle.

9. The apparatus as claimed in claim 5, further including means for resetting building of the data eye signal.

10. The apparatus as claimed in claim 9, wherein said memory storage device is one or more of a DRAM device or other source synchronous interface device.

11. A method for tracking a data eye window of a capture device receiving a plurality of data bit signals to be captured from a memory storage device, said capture device further receiving a strobe signal for latching the plurality of data bit signals at said capture device, said method comprising:

receiving, at a balanced tree network, each of the plurality of data bit signals comprising data bits input from the memory storage device, and generating an output signal associated with said plurality of data bit signals;

implementing a tapped inverter chain responsive to said output signal for generating a persistent data eye signal; and

adjusting said strobe signal associated with data eye centering in accordance with said persistent data eye signal;

wherein said tapped inverter chain comprises;

a serial connection of n number of inverter devices, each of the inverter devices providing a fixed delay time interval, and each of the inverter devices providing a respective output signal;

n number of latch devices, each latch device being associated with a respective inverter device for latching a respective output signal from each of the inverter devices; and

n−

1 number of comparison devices, each comparison device receiving a respective latched output signal from one of the latch devices, each comparison device receiving a latched output signal of a next latch device, and each comparison device determining a presence or an absence of a transition at a delay element interval resolution;

wherein n is an integer greater than 1.

12. The method as claimed in claim 11, further comprising, prior to said receiving step, a step of:

aligning one or more of said plurality of data bit signals according to a slowest received data bit signal prior to input to said balanced tree network.

13. The method as claimed in claim 11, further comprising:

latching an output of each respective comparison device, said persistent data eye signal represented as a series of latched data bits output from said tapped inverter chain.

14. The method as claimed in claim 11, wherein each tap along said tapped inverter chain represents a time accumulation for building said persistent data eye signal, said method further comprising:

locating a transition present along said tapped inverter chain, said transition indicating an edge of said data eye window.

15. The method as claimed in claim 14, further comprising:

detecting movement of the location of the transition along said tapped inverter chain for indicating a persistent data eye signal time shift relative to a centered data eye position; and

adjusting said strobe signal in accordance with said time shift.

16. The method as claimed in claim 14, further comprising:

updating said persistent data eye signal every valid data transfer cycle.

17. The method as claimed in claim 14, further comprising:

resetting building of the data eye window.

18. A computer program storage device, readable by machine, tangibly embodying a program of instructions executable by a machine to perform method steps for tracking a data eye window of a capture device receiving a plurality of data bit signals to be captured from a memory storage device, said capture device further receiving a strobe signal for latching the plurality of data bit signals at said capture device, said method steps comprising:

receiving, at a balanced tree network, each of the plurality of data bit signals comprising data bits input from the memory storage device, and generating an output signal associated with said plurality of data bit signals;

implementing a tapped inverter chain responsive to said output signal for generating a persistent data eye signal; and

adjusting said strobe signal associated with data eye centering in accordance with said persistent data eye signal;

wherein said tapped inverter chain comprises;

a serial connection of n number of inverter devices, each of the inverter devices providing a fixed delay time interval, and each of the inverter devices providing a respective output signal;

n number of latch devices, each latch device being associated with a respective inverter device for latching a respective output signal from each of the inverter devices; and

n−

1 number of comparison devices, each comparison device receiving a respective latched output signal from one of the latch devices, each comparison device receiving a latched output signal of a next latch device, and each comparison device determining a presence or an absence of a transition at a delay element interval resolution;

wherein n is an integer greater than 1.

19. The program storage device readable by a machine as claimed in claim 18, further comprising:

latching an output of each respective comparison device, said persistent data eye signal represented as a series of latched data bits output from said tapped inverter chain.

20. The program storage device readable by a machine as claimed in claim 18, wherein each tap along said tapped inverter chain represents a time accumulation for building said persistent data eye signal, said method steps further comprising:

locating a transition present along said tapped inverter chain, said transition indicating an edge of said data eye window.

21. The program storage device readable by a machine as claimed in claim 20, further comprising:

detecting movement of the location of the transition along said tapped inverter chain for indicating a persistent data eye signal time shift relative to a centered data eye position; and

adjusting said strobe signal in accordance with said time shift.

22. The program storage device readable by a machine as claimed in claim 18, further comprising, prior to said receiving step, a step of:

aligning one or more of said plurality of data bit signals to ensure alignment with a slowest received data bit signal prior to input to said balanced tree network.