July 29, 2010 PCN Number: 1013 PCN Change Level: Minor Subject: RTAX-S/SL and AX Enhanced Minimum Delay (EMD) Dear Customer, We have recently discovered an inaccuracy in Actel’s Libero® Integrated Design Environment (IDE) static timing analysis tool, SmartTime, which can cause inaccurate reporting of timing characteristics for RTAX-S/SL and Axcelerator® devices under specific circumstances. The software inaccuracy is described below along with a suggested workaround. Description of the Issue Enhanced Minimum Delay (EMD) is a delay calculation methodology introduced in Actel’s static timing analysis to compute lower bound delays on gates and nets. This is necessary for a conservative hold check (minimum delay analysis) during which the tightest timing margin (slack) is computed. During a hold check with EMD, SmartTime is not able to compute the tightest timing margin (slack) for the following conditions: • A reg-to-reg hold analysis on paths using an opposite edge clocking scheme • An external hold analysis with an external source register and internal sink register using an opposite edge clocking scheme Inaccurate timing numbers are returned only for minimum delay calculation under worst case operating conditions. The other conditions (minimum delay, best case; maximum delay, best case; maximum delay, worst case) return accurate results. It is important to note that this inaccuracy does not occur on an undetected violated timing path unless the clock is using regular routing resources (not dedicated globals) and the skew is at larger than half a period. The following is an example illustrating the problem: Data Delay Source Register Clock Insertion Delay Sink Register Clock Insertion Delay Figure 1. Sample Design Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 Part No. 54400089-0 In this example, the hold time check will be the following: • Arrival time is equal to the clock insertion delay to the source register plus data path delay. • Required time is the clock constraint plus the clock insertion delay of the sink register plus hold time of the sink register. • Clock constraint is the delay difference between the launching edge and the edge prior to the capturing edge. For a 50% duty cycle clock, it is equal to T/2 if T is the clock period. • Slack is equal to the arrival time minus the required time. Table 1 shows the results for different operating conditions on an implementation of this design on a RTAX250S/SL STD, with MIL operating conditions and the required clock period set to 100 MHz (delays are in ns). Operating Conditions Best Worst Worst EMD Y Y N Table 1. Analysis Results Sink Clock Clock Arrival Insertion Constraint 1.458 1.652 –5.000 2.689 2.849 –5.000 4.713 5.038 –5.000 Hold Required Slack 0 0 0 –3.348 –2.151 0.038 4.806 4.840 4.675 Because the clock constraint is fixed (does not change with operating conditions), higher slack results when higher delays are used; the worst slack results when there is no EMD (last row). Therefore, EMD must be turned off to obtain the worst slack. Workaround Actel recommends that customers perform timing analysis at all four corners – minimum delay, best case; minimum delay, worst case; maximum delay, best case; maximum delay, worst case. Using the Enhanced Min Delay tool is recommended for all of these with the exception of minimum delays, worst case. For this case, Actel recommends disabling the Enhanced Min Delay tool and performing timing analysis using SmartTime without the Enhanced Min Delay feature. Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 2 To turn off EMD, customers can set the EMD_70200rts variable to 0 in Designer by selecting Options > Variable Console and clicking Set value. Figure 2. Variables Console in Designer To re-enable EMD, close SmartTime and Designer, set the same variable to 1, and then restart Designer and SmartTime. This variable must be set before SmartTime is started for it to be effective. To verify whether EMD is being used, check the Summary in the GUI or the header of any report to see if "Using Enhanced Min Delay" is mentioned. The following is a list of affected devices. AX1000-1BG729 AX1000-1BG729I AX1000-1BG729M AX1000-1BGG729 AX1000-1BGG729I AX1000-1BGG729M AX1000-1CGS624M AX1000-1CQ352M AX1000-1FG484 AX1000-1FG484I AX1000-1FG484M Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 Table 2. Affected Devices AX1000 AX1000-1FGG896I AX1000-1FGG896M AX1000-1LG624M AX1000-2BG729 AX1000-2BG729I AX1000-2BGG729 AX1000-2BGG729I AX1000-2FG484 AX1000-2FG484I AX1000-2FG676 AX1000-2FG676I AX1000-BGG729I AX1000-BGG729M AX1000-CGS624M AX1000-CQ352M AX1000-FG484 AX1000-FG484I AX1000-FG484M AX1000-FG676 AX1000-FG676I AX1000-FG676M AX1000-FG896 3 AX1000-1FG676 AX1000-1FG676I AX1000-1FG676M AX1000-1FG896 AX1000-1FG896I AX1000-1FG896M AX1000-1FGG484 AX1000-1FGG484I AX1000-1FGG484M AX1000-1FGG676 AX1000-1FGG676I AX1000-1FGG676M AX1000-1FGG896 Table 2. Affected Devices (continued) AX1000-2FG896 AX1000-2FG896I AX1000-2FGG484 AX1000-2FGG484I AX1000-2FGG676 AX1000-2FGG676I AX1000-2FGG896 AX1000-2FGG896I AX1000-BG729 AX1000-BG729I AX1000-BG729M AX1000-BGG729 AX125-1CS180 AX125-1CS180I AX125-1CSG180 AX125-1CSG180I AX125-1FG256 AX125-1FG256I AX125-1FG324 AX125-1FG324I AX125-1FGG256 AX125-1FGG256I AX125-1FGG324 AX125-1FGG324I AX2000-1CGS624M AX2000-1CQ256M AX2000-1CQ352M AX2000-1FG1152 AX2000-1FG1152I AX2000-1FG1152M AX2000-1FG896 AX2000-1FG896I AX2000-1FG896M Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 AX125 AX125-2CS180 AX125-2CS180I AX125-2CSG180 AX125-2CSG180I AX125-2FG256 AX125-2FG256I AX125-2FG324 AX125-2FG324I AX125-2FGG256 AX125-2FGG256I AX125-2FGG324 AX125-2FGG324I AX2000 AX2000-1FGG896M AX2000-1LG624M AX2000-2FG1152 AX2000-2FG1152I AX2000-2FG896 AX2000-2FG896I AX2000-2FGG1152 AX2000-2FGG1152I AX2000-2FGG896 AX1000-FG896I AX1000-FG896M AX1000-FGG484 AX1000-FGG484I AX1000-FGG484M AX1000-FGG676 AX1000-FGG676I AX1000-FGG676M AX1000-FGG896 AX1000-FGG896I AX1000-FGG896M AX1000-LG624M AX125-CS180 AX125-CS180I AX125-CSG180 AX125-CSG180I AX125-FG256 AX125-FG256I AX125-FG324 AX125-FG324I AX125-FGG256 AX125-FGG256I AX125-FGG324 AX125-FGG324I AX2000-FG1152 AX2000-FG1152I AX2000-FG1152M AX2000-FG896 AX2000-FG896I AX2000-FG896M AX2000-FGG1152 AX2000-FGG1152I AX2000-FGG1152M 4 AX2000-1FGG1152 AX2000-1FGG1152I AX2000-1FGG1152M AX2000-1FGG896 AX2000-1FGG896I Table 2. Affected Devices (continued) AX2000-2FGG896I AX2000-CGS624M AX2000-CQ256M AX2000-CQ352M AX2000-FGG896 AX2000-FGG896I AX2000-FGG896M AX2000-LG624M AX250 AX250-1PQG208I AX250-1PQG208M AX250-2FG256 AX250-2FG256I AX250-2FG484 AX250-2FG484I AX250-2FGG256 AX250-2FGG256I AX250-2FGG484 AX250-2FGG484I AX250-2PQ208 AX250-2PQ208I AX250-2PQG208 AX250-2PQG208I AX250-CQ208M AX250-CQ352M AX250-FG256 AX250-FG256I AX250-FG256M AX250-FG484 AX250-FG484I AX250-FG484M AX250-FGG256 AX250-FGG256I AX250-FGG256M AX250-FGG484 AX250-FGG484I AX250-FGG484M AX250-PQ208 AX250-PQ208I AX250-PQ208M AX250-PQG208 AX250-PQG208I AX250-PQG208M AX500 AX500-1PQG208I AX500-1PQG208M AX500-2FG484 AX500-2FG484I AX500-2FG676 AX500-2FG676I AX500-2FGG484 AX500-2FGG484I AX500-2FGG676 AX500-2FGG676I AX500-2PQ208 AX500-FG484I AX500-FG484M AX500-FG676 AX500-FG676I AX500-FG676M AX500-FGG484 AX500-FGG484I AX500-FGG484M AX500-FGG676 AX500-FGG676I AX500-FGG676M AX250-1CQ208M AX250-1CQ352M AX250-1FG256 AX250-1FG256I AX250-1FG256M AX250-1FG484 AX250-1FG484I AX250-1FG484M AX250-1FGG256 AX250-1FGG256I AX250-1FGG256M AX250-1FGG484 AX250-1FGG484I AX250-1FGG484M AX250-1PQ208 AX250-1PQ208I AX250-1PQ208M AX250-1PQG208 AX500-1CQ208M AX500-1CQ352M AX500-1FG484 AX500-1FG484I AX500-1FG484M AX500-1FG676 AX500-1FG676I AX500-1FG676M AX500-1FGG484 AX500-1FGG484I AX500-1FGG484M Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 5 AX500-1FGG676 AX500-1FGG676I AX500-1FGG676M AX500-1PQ208 AX500-1PQ208I AX500-1PQ208M AX500-1PQG208 Table 2. Affected Devices (continued) AX500-2PQ208I AX500-2PQG208 AX500-2PQG208I AX500-CQ208M AX500-CQ352M AX500-FG484 5962-0422001QUA 5962-0422001QXC 5962-0422001QYC 5962-0422002QUA 5962-0422002QXC 5962-0422002QYC 5962-0422003QUA 5962-0422003QXC 5962-0422003QYC 5962-0422004QUA 5962-0422004QXC 5962-0422004QYC 5962-0422005QUA 5962-0422005QXC 5962-0422005QYC 5962-0422006QUA 5962-0422006QXC 5962-0422006QYC 5962-0422007QUA 5962-0422007QXC 5962-0422007QYC 5962-0422008QUA 5962-0422101QMC 5962-0422101QNA 5962-0422101QTA 5962-0422101QUC 5962-0422101QXC Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 RTAX1000S 5962-0422008QXC 5962-0422008QYC RTAX1000S-1CG624PROTO RTAX1000S-1CGS624B RTAX1000S-1CGS624E RTAX1000S-1CGS624EV RTAX1000S-1CQ352B RTAX1000S-1CQ352E RTAX1000S-1CQ352EV RTAX1000S-1CQ352PROTO RTAX1000S-1LG624B RTAX1000S-1LG624E RTAX1000S-1LG624EV RTAX1000S-1LG624PROTO RTAX1000S-CG624PROTO RTAX1000S-CGS624B RTAX1000S-CGS624E RTAX1000S-CGS624EV RTAX1000S-CQ352B RTAX1000S-CQ352E RTAX1000S-CQ352EV RTAX1000S-CQ352PROTO RTAX2000S 5962-0422108QTA 5962-0422108QUC 5962-0422108QXC 5962-0422108QYC RTAX2000S-1CG1152B AX500-PQ208 AX500-PQ208I AX500-PQ208M AX500-PQG208 AX500-PQG208I AX500-PQG208M RTAX1000SL-1CGS624B RTAX1000SL-1CGS624E RTAX1000SL-1CGS624EV RTAX1000SL-1CQ352B RTAX1000SL-1CQ352E RTAX1000SL-1CQ352EV RTAX1000SL-1LG624B RTAX1000SL-1LG624E RTAX1000SL-1LG624EV RTAX1000SL-CGS624B RTAX1000SL-CGS624E RTAX1000SL-CGS624EV RTAX1000SL-CQ352B RTAX1000SL-CQ352E RTAX1000SL-CQ352EV RTAX1000S-LG624B RTAX1000S-LG624E RTAX1000S-LG624EV RTAX1000S-LG624PROTO RTAX1000SL-LG624B RTAX1000SL-LG624E RTAX1000SL-LG624EV RTAX2000SL-1CG1152B RTAX2000SL-1CG1152E RTAX2000SL-1CG1152EV RTAX2000SL-1CGS624B RTAX2000SL-1CGS624E 6 5962-0422101QYC 5962-0422102QMC 5962-0422102QNA 5962-0422102QTA 5962-0422102QUC 5962-0422102QXC 5962-0422102QYC 5962-0422103QMC 5962-0422103QNA 5962-0422103QTA 5962-0422103QUC 5962-0422103QXC 5962-0422103QYC 5962-0422104QMC 5962-0422104QNA 5962-0422104QTA 5962-0422104QUC 5962-0422104QXC 5962-0422104QYC 5962-0422105QMC 5962-0422105QNA 5962-0422105QTA 5962-0422105QUC 5962-0422105QXC 5962-0422105QYC 5962-0422106QMC 5962-0422106QNA 5962-0422106QTA 5962-0422106QUC 5962-0422106QXC 5962-0422106QYC 5962-0422107QMC 5962-0422107QNA 5962-0422107QTA 5962-0422107QUC 5962-0422107QXC Table 2. Affected Devices (continued) RTAX2000S-1CG1152E RTAX2000SL-1CGS624EV RTAX2000S-1CG1152EV RTAX2000SL-1CQ256B RTAX2000S-1CG1152PROTO RTAX2000SL-1CQ256E RTAX2000S-1CG624PROTO RTAX2000SL-1CQ256EV RTAX2000S-1CGS624B RTAX2000SL-1CQ352B RTAX2000S-1CGS624E RTAX2000SL-1CQ352E RTAX2000S-1CGS624EV RTAX2000SL-1CQ352EV RTAX2000S-1CQ256B RTAX2000SL-1LG1152B RTAX2000S-1CQ256E RTAX2000SL-1LG1152E RTAX2000S-1CQ256EV RTAX2000SL-1LG1152EV RTAX2000S-1CQ256PROTO RTAX2000SL-1LG624B RTAX2000S-1CQ352B RTAX2000SL-1LG624E RTAX2000S-1CQ352E RTAX2000SL-1LG624EV RTAX2000S-1CQ352EV RTAX2000SL-CG1152B RTAX2000S-1CQ352PROTO RTAX2000SL-CG1152E RTAX2000S-1LG1152B RTAX2000SL-CG1152EV RTAX2000S-1LG1152E RTAX2000SL-CGS624B RTAX2000S-1LG1152EV RTAX2000SL-CGS624E RTAX2000S-1LG1152PROTO RTAX2000SL-CGS624EV RTAX2000S-1LG624B RTAX2000SL-CQ256B RTAX2000S-1LG624E RTAX2000SL-CQ256E RTAX2000S-1LG624EV RTAX2000SL-CQ256EV RTAX2000S-1LG624PROTO RTAX2000SL-CQ352B RTAX2000S-CG1152B RTAX2000SL-CQ352E RTAX2000S-CG1152E RTAX2000SL-CQ352EV RTAX2000S-CG1152EV RTAX2000S-LG1152B RTAX2000S-CG1152PROTO RTAX2000S-LG1152E RTAX2000S-CG624PROTO RTAX2000S-LG1152EV RTAX2000S-CGS624B RTAX2000S-LG1152PROTO RTAX2000S-CGS624E RTAX2000S-LG624B RTAX2000S-CGS624EV RTAX2000S-LG624E RTAX2000S-CQ256B RTAX2000S-LG624EV RTAX2000S-CQ256E RTAX2000S-LG624PROTO RTAX2000S-CQ256EV RTAX2000SL-LG1152B RTAX2000S-CQ256PROTO RTAX2000SL-LG1152E RTAX2000S-CQ352B RTAX2000SL-LG1152EV Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 7 5962-0422107QYC 5962-0422108QMC 5962-0422108QNA 5962-0421901QUA 5962-0421901QXC 5962-0421901QYC 5962-0421901QZC 5962-0421902QUA 5962-0421902QXC 5962-0421902QYC 5962-0421902QZC 5962-0421903QUA 5962-0421903QXC 5962-0421903QYC 5962-0421903QZC 5962-0421904QUA 5962-0421904QXC 5962-0421904QYC 5962-0421904QZC 5962-0421905QUA 5962-0421905QXC 5962-0421905QYC 5962-0421905QZC 5962-0421906QUA 5962-0421906QXC 5962-0421906QYC 5962-0421906QZC 5962-0421907QUA 5962-0421907QXC 5962-0421907QYC 5962-0421907QZC 5962-0421908QUA 5962-0421908QXC Table 2. Affected Devices (continued) RTAX2000S-CQ352E RTAX2000SL-LG624B RTAX2000S-CQ352EV RTAX2000SL-LG624E RTAX2000S-CQ352PROTO RTAX2000SL-LG624EV RTAX250S 5962-0421908QYC RTAX250S-CQ352PROTO 5962-0421908QZC RTAX250SL-1CG624B RTAX250S-1CG624B RTAX250SL-1CG624E RTAX250S-1CG624E RTAX250SL-1CG624EV RTAX250S-1CG624EV RTAX250SL-1CQ208B RTAX250S-1CG624PROTO RTAX250SL-1CQ208E RTAX250S-1CQ208B RTAX250SL-1CQ208EV RTAX250S-1CQ208E RTAX250SL-1CQ352B RTAX250S-1CQ208EV RTAX250SL-1CQ352E RTAX250S-1CQ208PROTO RTAX250SL-1CQ352EV RTAX250S-1CQ352B RTAX250SL-1LG624B RTAX250S-1CQ352E RTAX250SL-1LG624E RTAX250S-1CQ352EV RTAX250SL-1LG624EV RTAX250S-1CQ352PROTO RTAX250SL-CG624B RTAX250S-1LG624B RTAX250SL-CG624E RTAX250S-1LG624E RTAX250SL-CG624EV RTAX250S-1LG624EV RTAX250SL-CQ208B RTAX250S-1LG624PROTO RTAX250SL-CQ208E RTAX250S-CG624B RTAX250SL-CQ208EV RTAX250S-CG624E RTAX250SL-CQ352B RTAX250S-CG624EV RTAX250SL-CQ352E RTAX250S-CG624PROTO RTAX250SL-CQ352EV RTAX250S-CQ208B RTAX250S-LG624B RTAX250S-CQ208E RTAX250S-LG624E RTAX250S-CQ208EV RTAX250S-LG624EV RTAX250S-CQ208PROTO RTAX250S-LG624PROTO RTAX250S-CQ352B RTAX250SL-LG624B RTAX250S-CQ352E RTAX250SL-LG624E RTAX250S-CQ352EV RTAX250SL-LG624EV Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 8 Table 2. Affected Devices (continued) RTAX4000S RTAX4000S-1CG1272B RTAX4000S-CG1272EV RTAX4000SL-1LG1272EV RTAX4000S-1CG1272E RTAX4000S-CG1272PROTO RTAX4000SL-CG1272B RTAX4000S-1CG1272EV RTAX4000S-CQ352B RTAX4000SL-CG1272E RTAX4000S-1CG1272PROTO RTAX4000S-CQ352E RTAX4000SL-CG1272EV RTAX4000S-1CQ352B RTAX4000S-CQ352EV RTAX4000SL-CQ352B RTAX4000S-1CQ352E RTAX4000S-CQ352PROTO RTAX4000SL-CQ352E RTAX4000S-1CQ352EV RTAX4000SL-1CG1272B RTAX4000SL-CQ352EV RTAX4000S-1CQ352PROTO RTAX4000SL-1CG1272E RTAX4000S-LG1272B RTAX4000S-1LG1272B RTAX4000SL-1CG1272EV RTAX4000S-LG1272E RTAX4000S-1LG1272E RTAX4000SL-1CQ352B RTAX4000S-LG1272EV RTAX4000S-1LG1272EV RTAX4000SL-1CQ352E RTAX4000S-LG1272PROTO RTAX4000S-1LG1272PROTO RTAX4000SL-1CQ352EV RTAX4000SL-LG1272B RTAX4000S-CG1272B RTAX4000SL-1LG1272B RTAX4000SL-LG1272E RTAX4000S-CG1272E RTAX4000SL-1LG1272E RTAX4000SL-LG1272EV Long Term Solution Actel is working to improve this issue of inaccurate timing results returned when Enhanced Min Delays are enabled for minimum delay, worst case conditions. We expect that accurate results will be provided in software versions beginning with Libero IDE v9.0 SP2, to be released in August 2010. If you have any additional questions, please do not hesitate to contact Actel’s ITAR Technical support at http://www.actel.com/mycases or [email protected]. Yours Sincerely, Actel Corporation Actel Corporation 2061 Stierlin Court, Mountain View, CA 94043 Phone: 650.318.4200 Fax 650.318.4600 9