Compressed scan chains with three input mask gates and registers
First Claim
1. An electronic scan circuitry comprising:
- (a) decompressor circuitry having a serial data input line and parallel data output lines;
(b) scan chains, each scan chain having a scan chain input coupled to one parallel data output line and having a scan chain output;
(c) first masking circuitry having first masking inputs coupled to a first group of the scan chain outputs, the first masking circuitry including;
(i) first gates, each first gate having a first input connected to a first masking input, a second input coupled to a first qualify line, a third input, and a first masking output; and
(ii) first registers coupled in series, each first register having a serial input and an output connected to the third input of a first gate;
(d) second masking circuitry having second masking inputs coupled to a second group of the scan chain outputs, the second masking circuitry including;
(i) second gates, each second gate having a first input connected to a second masking input, a second input coupled to a second qualify line separate from the first qualify line, a third input, and a second masking output; and
(ii) second registers coupled in series with the first registers, each second register having a serial input and an output connected to a third input of the second gates; and
(e) compactor circuitry having parallel compactor inputs coupled to the first masking outputs and the second masking outputs, and having a serial compactor output.
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Accused Products
Abstract
Electronic scan circuitry includes a decompressor (510), a plurality of scan chains (520.i) fed by the decompressor (510), a scan circuit (502, 504) coupled to the plurality of scan chains (520.i) to scan them in and out, a masking circuit (590) fed by the scan chains (520.i), and a scannable masking qualification circuit (550, 560, 580) coupled to the masking circuit (590), the masking qualification circuit (550, 560, 580) scannable by scan-in of bits by the decompressor (510) along with scan-in of the scan chains (520.i), and the scannable masking qualification circuit (550, 560, 580) operable to hold such scanned-in bits upon scan-out of the scan chains through the masking circuit (590). Other scan circuitry, processes, circuits, devices and systems are also disclosed.
37 Citations
8 Claims
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1. An electronic scan circuitry comprising:
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(a) decompressor circuitry having a serial data input line and parallel data output lines; (b) scan chains, each scan chain having a scan chain input coupled to one parallel data output line and having a scan chain output; (c) first masking circuitry having first masking inputs coupled to a first group of the scan chain outputs, the first masking circuitry including; (i) first gates, each first gate having a first input connected to a first masking input, a second input coupled to a first qualify line, a third input, and a first masking output; and (ii) first registers coupled in series, each first register having a serial input and an output connected to the third input of a first gate; (d) second masking circuitry having second masking inputs coupled to a second group of the scan chain outputs, the second masking circuitry including; (i) second gates, each second gate having a first input connected to a second masking input, a second input coupled to a second qualify line separate from the first qualify line, a third input, and a second masking output; and (ii) second registers coupled in series with the first registers, each second register having a serial input and an output connected to a third input of the second gates; and (e) compactor circuitry having parallel compactor inputs coupled to the first masking outputs and the second masking outputs, and having a serial compactor output. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification