Tap gating scan register, comparator with expected data flip flop
First Claim
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1. A device comprising:
- (a) a scan data input;
(b) a test clock input;
(c) a test mode select input;
(d) test access port circuitry having an input coupled to the test clock input, an input coupled to the test mode select input, a scan clock output, and a control output;
(e) a scan register having an input coupled to the scan data input, an input coupled to the scan clock output, a gated scan enable input, and a scan output;
(f) an inverter having an input coupled to the test clock input and an inverted test clock output;
(g) an expected data flip flop having an input coupled to the scan data input. an input coupled to the inverted test clock output, and an expected data output;
(h) a second flip flop having an input coupled to the test mode select input, an input coupled to the inverted test clock output, and a data output;
(i) gate circuitry having an input coupled to the data output of the second flip flop, an input coupled to the control output, and a gated scan enable output coupled to the gated scan enable input; and
(j) compare circuitry having a first input coupled to the scan output of the scan register and a second input coupled to the expected data output.
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Abstract
The disclosure describes a novel method and apparatus for providing expected data, mask data, and control signals to scan test architectures within a device using the falling edge of a test/scan clock. The signals are provided on device leads that are also used to provide signals to scan test architectures using the rising edge of the test/scan clock. According to the disclosure, device test leads serve to input different test signals on the rising and falling edge of the test/scan clock which reduces the number of interconnects between a tester and the device under test.
31 Citations
11 Claims
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1. A device comprising:
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(a) a scan data input; (b) a test clock input; (c) a test mode select input; (d) test access port circuitry having an input coupled to the test clock input, an input coupled to the test mode select input, a scan clock output, and a control output; (e) a scan register having an input coupled to the scan data input, an input coupled to the scan clock output, a gated scan enable input, and a scan output; (f) an inverter having an input coupled to the test clock input and an inverted test clock output; (g) an expected data flip flop having an input coupled to the scan data input. an input coupled to the inverted test clock output, and an expected data output; (h) a second flip flop having an input coupled to the test mode select input, an input coupled to the inverted test clock output, and a data output; (i) gate circuitry having an input coupled to the data output of the second flip flop, an input coupled to the control output, and a gated scan enable output coupled to the gated scan enable input; and (j) compare circuitry having a first input coupled to the scan output of the scan register and a second input coupled to the expected data output. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An integrated circuit scan test architecture comprising:
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(a) combinational logic having parallel stimulus inputs and parallel response outputs; (b) a scan data input, a test clock input, and a test mode select input; (c) test access port circuitry having a state machine operating in states, an input coupled to the test clock input, an input coupled to the test mode select input, a scan clock output, and a control output; (d) a scan register having an input coupled to the scan data input, an input coupled to the scan clock output, parallel stimulus outputs coupled to the parallel stimulus inputs, parallel response inputs coupled to the parallel response outputs, a gated scan enable input, and a scan output; (e) an inverter having an input coupled to the test clock input and an inverted test clock output; (f) an expected data flip flop having an input coupled to the scan data input. an input coupled to the inverted test clock output, and an expected data output; (g) a second flip flop having an input coupled to the test mode select input, an input coupled to the inverted test clock output, and a data output; (h) gate circuitry having an input coupled to the data output of the flip flop, an input coupled to the control output, and a gated scan enable output coupled to the gated scan enable input; and (i) compare circuitry having a first input coupled to the scan output of the scan register and an input coupled to the expected data output. - View Dependent Claims (8, 9, 10, 11)
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Specification