Oscillation based access time measurement

Abstract

An embodiment of the invention is a method for measuring access time where the frequency of a ring oscillator is measured with and without a device under test 1 in the ring. Those two frequencies are compared to calculate the access time of the device under test 1. Another embodiment of the invention is circuitry 25 that measures the frequency of a ring oscillator with and without a device under test 1. Again the two frequencies are compared to calculate the access time of the device under test 1.

1 . (Cancelled)  
     
     
         2 . (Cancelled)  
     
     
         3 . (Cancelled)  
     
     
         4 . An integrated circuit comprising: 
 an on-chip measurement circuit, said on-chip measurement circuit containing a ring oscillator that facilitates frequency measurements both with circuitry under test in said ring oscillator and also free-running with said circuitry under test out of said ring oscillator.    
     
     
         5 . The integrated circuit of  claim 4  wherein the access time of said circuitry under test is the difference between said frequencies.  
     
     
         6 . The integrated circuit of  claim 4  wherein said ring oscillator contains a pulse generator.  
     
     
         7 . The integrated circuit of  claim 6 , wherein said pulse generator creates a clock pulse for said circuitry under test every time the output changes.  
     
     
         8 . The integrated circuit of  claim 4 , wherein said frequency measurements are performed at the output of a frequency divider circuit coupled to said ring oscillator.  
     
     
         9 . The integrated circuit of  claim 8  wherein the access time of said circuitry under test is the difference between said frequency measurements.  
     
     
         10 . A memory comprising: 
 an on-chip measurement circuit, said on-chip measurement circuit containing a ring oscillator that facilitates frequency measurements both with circuitry under test in said ring oscillator and also free-running with said circuitry under test out of said ring oscillator.    
     
     
         11 . The integrated circuit of  claim 10  wherein the access time of said circuitry under test is the difference between said frequencies.  
     
     
         12 . The integrated circuit of  claim 10  wherein said ring oscillator contains a pulse generator.  
     
     
         13 . The integrated circuit of  claim 12 , wherein said pulse generator creates a clock pulse for said circuitry under test every time the output changes.  
     
     
         14 . The integrated circuit of  claim 10 , wherein said frequency measurements are performed at the output of a frequency divider circuit coupled to said ring oscillator.  
     
     
         15 . The integrated circuit of  claim 14  wherein the access time of said circuitry under test is the difference between said frequency measurements.  
     
     
         16 . An integrated circuit comprising: 
 an on-chip measurement circuit, said on-chip measurement circuit containing a ring oscillator that facilitates frequency measurements both with memory circuitry in said ring oscillator and also free-running with said memory circuitry out of said ring oscillator.    
     
     
         17 . The integrated circuit of  claim 16  wherein the access time of said memory circuitry is the difference between said frequencies.  
     
     
         18 . The integrated circuit of  claim 16  wherein said ring oscillator contains a pulse generator.  
     
     
         19 . The integrated circuit of  claim 18 , wherein said pulse generator creates a clock pulse for said memory circuitry every time the output changes.  
     
     
         20 . The integrated circuit of  claim 16 , wherein said frequency measurements are performed at the output of a frequency divider circuit coupled to said ring oscillator.  
     
     
         21 . The integrated circuit of  claim 20  wherein the access time of said memory circuitry is the difference between said frequency measurements.