© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper #15 1 Ted Eaton coerced by the late Bill Eklow 9/15/ Cross-over issue
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper # test Receivers Differential? The standard tells us Rules a) All AC pins (see 4.1) that receive input data, whether they are single-ended or one leg of a differential pair, shall have exactly one test receiver function monitoring the mission pin signal. BSDL tells us : List all DIFF + pins in the AIO_PIN_BEHAVIOR Infer.6 behavior on – pins using PORT_GROUPING The ATPG tools don’t bother to care A DIFF is a DIFF is a DIFF
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper #15 3 ATPG Does this great
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper # test Receivers Differential? Board Layout rules tell us sometimes it is better to route + to – ASIC design says ok… connect the pins as you need and we will invert + and – in functional mode and.6 is single ended so who cares. The ATPG tools don’t bother to care “A DIFF is a DIFF is a DIFF”
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper #15 5 ATPG Does this Great… WAIT!!!! A DIFF is NOT a DIFF
© 2008 Cisco Systems, Inc. All rights reserved.Cisco ConfidentialPaper #15 6