Apparatus and method for unambiguous counter reading

Claim 1

For use in effecting an unambiguous reading of the number stored in a binary counter to avoid errors caused by the counter changing its state during the reading, the combination comprising; transfer means interconnected between individual orders of said binary counter and a first register, means for selectively activating said transfer means to transfer a representation of the instantaneous condition of said binary counter into said first register for registering a first reading, means for selectively interconnecting said transfer means between said orders of said counter and a second register, means for selectively activating said transfer means to transfer a representation of the instantaneous condition of said counter into said second register for registering a second reading immediately after registration of said first reading, comparator means operative subsequently to the reading of said counter into said second register for comparing the content of said first and second registers, means connected to said comparator means and selectively operative in response thereto to activate said transfer means immediately after the registration of said second reading to make a third transfer of the condition of said counter to one of said registers only if the condition of said counter during said first transfer is not equal to the condition of said counter during said second transfer, and means connected to transmit one of two consecutive identical readings of said counter for use as the desired unambiguous reading of the counter.

Claim 3

The method of unambiguously reading the ''''number stored in a binary counter to avoid errors caused by the counter changing its state during the reading'''' comprising the steps of effecting a first reading of the content of said counter, storing the result of said first reading, effecting a second reading of the content of said counter immediately after the completion of said first reading, storing the result of said second reading, comparing the results of said first and second readings, and effecting a third reading of said counter in response to said comparison immediately after the completion of said second reading only when the results of said first and second readings are not identical, and transmitting one of two consecutive identical readings of said counter as the desired unambiguous reading of the counter.

Claim 4

The method of unambiguously reading the ''''number stored in a binary counter to avoid errors caused by the counter changing its state during the reading'''' comprising the steps of effecting a first reading of the content of said counter, storing the result of said first reading, effecting a second reading of the content of said counter immediately after the completion of said first reading, storing the result of said second reading, comparing the results of said first and second readings, and effecting a third reading of said counter in response to said comparison immediately after the completion of said second reading only when the results of said first and second readings are not identical, and transmitting one of two consecutive identical readings of said counter as the desired unambiguous reading of the counter.