Data link test method and apparatus

Claim 2

In digital signal apparatus including a plurality of cascaded logic elements forming a shift register stage which has an output and which has a signal port coupled to an input of the cascade arrangement and to an auxiliary input intermediate a pair of logic elements in the cascade arrangement and which operates through a selected sequence of digital signals in response to signals applied to the signal port from the output of the cascade arrangement, the method of selectively synchronizing the operation of the cascade arrangement of logic elements to the operation of a source which produces digital signals in said selected sequence comprising the steps of: connecting the signal port to receive the digital signals from the source to alter the signal appearing at the output of the cascade arrangement; comparing the digital signal received from the source with the signal at the output of the cascade arrangement for determining the establishment of a predetermined relationship between the sequences thereof; and altering the connection of the signal port to receive the output of the cascade arrangement in response to establishment of said predetermined relationship for operating the cascade arrangement of logic elements through said selected sequence in synchronism with operation of the source through the same selected sequence.

Claim 3

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states.

Claim 4

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states.

Claim 5

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input Of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states; second means including said plural number of logic elements, each having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; coupling means for said second means coupling the output of at least one logic element of the second means to the input of at least another logic element of the second means for operating recurringly through a sequence of logic states which is similar to a sequence of logic states produced during recurring-sequence operation of the first means; and circuit means including a digital signalling circuit for applying the recurring sequence of logic states from the second means to the signal input of the first means.

Claim 6

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input Of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states; second means including said plural number of logic elements, each having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; coupling means for said second means coupling the output of at least one logic element of the second means to the input of at least another logic element of the second means for operating recurringly through a sequence of logic states which is similar to a sequence of logic states produced during recurring-sequence operation of the first means; and circuit means including a digital signalling circuit for applying the recurring sequence of logic states from the second means to the signal input of the first means.

Claim 7

Digital signal apparatus as in claim 3 comprising: control means coupled to said signal input and to the output of said logic element which succeeds the auxiliary signal input of the first means for controlling the selection of the signal at said signal input for synchronizing the operation of the logic elements of the first and second means through a sequence of logic states, and the output signal of the first means for providing an indication of error in the transmission of a sequence of logic states from the second means to the first means through said digital signalling circuit.

Claim 8

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states; gate means coupled to receive the signal at said signal input and the signal at said output of a logic element of the first means for producing an error output signal as the combination of such signals; additional means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; coupling means coupling the output of one of the logic elements of said additional means to the input of another logic element of said additional means for forming a primary signal circuit of cascaded Logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements of said additional means, the arrangement of logic elements and auxiliary signal inputs in said first and additional means being substantially similar; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of said additional means, and operable to apply signals on said auxiliary signal circuit to the input of said one logic element and to said auxiliary signal input; means coupled to the auxiliary signal circuit of said additional means for applying thereto said error output signal from the gate means; and control input means coupled to an output of a logic element of said additional means succeeding said auxiliary signal input in the primary signal circuit of said additional means, and coupled to receive said error output signal for controlling the selection in the first means of either the signal present at said signal input or said signal present at the output of said logic element of the first means which succeeds said auxiliary signal input.

Claim 9

Digital signal apparatus comprising: first means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; and including coupling means coupling the output of one of the logic elements of the first means to the input of another logic element of the first means for forming a primary signal circuit of cascaded logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements; a signal input; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of the first means; said auxiliary signal circuit being operable to apply to the auxiliary signal input and to the input of said one logic element a selected one of either a signal present at said signal input for operation through a sequence of logic states in response to signals at said signal input or a signal present at the output of a logic element which succeeds the auxiliary signal input in the cascaded logic elements of the primary signal circuit for recurring operation through a sequence of logic states; gate means coupled to receive the signal at said signal input and the signal at said output of a logic element of the first means for producing an error output signal as the combination of such signals; additional means including a plural number of logic elements, each of said logic elements having an input and an output and being operable to produce a signal at said output a selected time interval after the application of a signal to said input; coupling means coupling the output of one of the logic elements of said additional means to the input of another logic element of said additional means for forming a primary signal circuit of cascaded Logic elements and for providing at least one auxiliary signal input between a pair of said plural number of logic elements of said additional means, the arrangement of logic elements and auxiliary signal inputs in said first and additional means being substantially similar; at least one auxiliary signal circuit coupled to an auxiliary signal input and to the input of a logic element which precedes the auxiliary signal input in the cascaded logic elements of the primary signal circuit of said additional means, and operable to apply signals on said auxiliary signal circuit to the input of said one logic element and to said auxiliary signal input; means coupled to the auxiliary signal circuit of said additional means for applying thereto said error output signal from the gate means; and control input means coupled to an output of a logic element of said additional means succeeding said auxiliary signal input in the primary signal circuit of said additional means, and coupled to receive said error output signal for controlling the selection in the first means of either the signal present at said signal input or said signal present at the output of said logic element of the first means which succeeds said auxiliary signal input.

Claim 10

Digital signal apparatus as in claim 5 wherein said control input means also includes: a first gate coupled to receive signals at the outputs of the logic elements of said additional means for producing a first reference output signal as a logic combination of such outputs; a second gate coupled to receive the output of a logic element of said additional means succeeding said auxiliary signal input in the primary signal circuit of the additional means, and coupled to receive said error output signal for producing a second reference output signal; and a synchronizing circuit responsive to the recurrence of a logic combination of the first and second reference output signals a number of times greater than said plural number of logic elements of said first means for operating said auxiliary signal circuit of the first means to receive signal present at said signal input for synchronizing the operation of the logic elements of the first means through a sequence of logic states with a sequence of logic states appearing on said signal input.