Leveraging Software to Enhance Timing Analysis for Actel RTAX-S Devices

1. Leveraging Software to Enhance Timing Analysis for Actel RTAX-S Devices Johnny Chung Corporate Applications Engineering Actel Corporation MAPLD 2005

2. SmartTime • Achieve timing closure easier with Actel’s gate-level static timing analysis tool • fully integrated within Actel’s software solution • Enables complete timing analysis and timing constraints editing for RTAX-S designs to achieve desired performance • Ensure all timing constraints are met • Ensure design operates at the desired speed with the right amount of margin across all operating condition variations • Provides a selection of analysis types that enables the following: • Find the minimum cycle time that does not result in a timing violation • Identify paths with timing violations • Analyze delays of paths that have no timing constraints • Perform inter-clock domain timing verification • Perform maximum and minimum delay analysis for setup and hold checks • checks the timing requirements for violations while taking into account timing exceptions such as multicycle or false paths

3. SmartTime • Timing Constraints Editor • You can add or modify timing constraints on a specific pin (for example, clock constraint) or on a specific set-of-paths (for example, maximum delay constraint) for your timing requirements and timing exceptions • User-friendly visual dialog boxes • Timing Analyzer • You can browse through the design’s various clock domains to examine the timing paths and identify those violating the timing requirements • You can also add or modify constraints for your timing requirements and timing exceptions

4. SmartTime New Features • Provides a larger number of work-saving features compared to previous timing tool • External Setup/Hold • includes an external setup/hold domain browser to show the delay more clearly than previous timing tool • Input Delay Constraint • can be set according to External Setup/Hold constraint or as Input delay constraint • Visual constraint dialogs • Clock to Output Delay • SmartTime shows the entire path delay from the clock source through the clock pin of the register to the output port, an improvement over the previous timing tool

5. SmartTime New Features • Provides a larger number of work-saving features compared to previous timing tool • Maximum Delay Constraint Priority • Maximum delay is seen as an exception to the clock constraint • Maximum delay constraint always has a higher priority than the clock constraint • Inter-Clock Domain • SmartTime allows the inter-clock domain analysis, an improvement over the previous timing tool • Flexibility in clock domain selection

6. Setup Check in SmartTime to Aid RTAX-S Timing Analysis • Setup Check • Arrival time = Launch edge (0) + max Clock to FF1 + max Data path • Required time = Capture edge (T) + min Clock to FF2 – Setup of FF2 • Slack = Required – Arrival = Violation if < 0

7. Setup Check w/ Multicycle Paths for RTAX-S Timing Analysis • Add MulticycleConstraint • Fields are pre-filled with the path information

8. Setup Check w/ Multicycle Paths for RTAX-S Timing Analysis • Setup Check • Arrival time = Launch edge (0) + max Clock to FF1 + max Data path • Required time = Capture edge (2T) + min Clock to FF2 – Setup of FF2 • Slack = Required – Arrival = Violation if < 0

9. Hold Check in SmartTime for RTAX-S Timing Analysis • Hold Check • Arrival time = Launch edge (0) + min Clock to FF1 + min Data path • Required time = Capture edge (0) + max Clock to FF2 + Hold of FF2 • Slack = Arrival – Required = Violation if < 0

10. Setup Check w/ Input Delay • Enter Constraint as Input Delay

11. Setup Check w/ Input Delay • Enter Constraint as External Setup/Hold

12. Setup Check w/ Input Delay in SmartTime for RTAX-S Timing Analysis • Setup Check • Arrival time = Launch edge (0) + max input delay + max Data path • Required time = Capture edge (T) + min Clock to FF1 – Setup of FF1 • Slack = Required – Arrival = Violation if < 0

13. Setup Check w/ Output Delay • Enter Constraint as Output Delay

14. Setup Check w/ Output Delay • Enter Constraint as Clock-to-Out

15. Setup Check w/ Output Delay in SmartTime for RTAX-S Timing Analysis • Setup Check • Arrival time = Launch edge (0) + max Data path • Required time = Capture edge (T) – Output Delay • Slack = Required – Arrival = Violation if < 0

16. Inter-Clock Domains Timing Analysis • Larger designs may require interfacing between different clock domains • Designs with inter-clock domains requires timing verification between the related clocks • When functional paths exist across two clock domains, accurate specification of both clocks is required to allow a valid inter-clock domain timing check • This is important especially when the clocks are specified with different waveforms and frequencies • First step is to consider whether the inter-clock domain paths are false or functional • If functional, setup and hold check must be performed

17. Inter-Clock Domains Timing Analysis • SmartTime timing analyzer for Actel RTAX-S FPGA timing analysis • SmartTime looks at the relationship between the active clock edges over a full repeating cycle, equal to the least common multiple of the two clock periods • The new common period represents a full repeating cycle (or pattern) of the two clock waveforms • For setup check, the tightest relation launch-capture is considered to ensure that the data arrives before the capture edge • The hold check verifies that a setup relationship is not overwritten by a following data launch setup2 setup1 Repeating cycle

18. Inter-Clock Domains in SmartTime

19. Timing Report Options • Timing Report can be generated with different options, providing flexibility and customization for users • General setup • Filter report by slack threshold • Report using Maximum or Minimum delay analysis • Paths and Sets • Limit the number of paths to be reported in the timing report • Clock Domains • Limit reporting of clock domains to specific domains • More clear reporting format • Improvement over previous timing tool

20. Timing Report Summary • Key enhancements from old timing report vs. new timing report • Old report format • New report format shows more detail for the specified path $Registers(Clock):$ClockPins() to $Registers(Clock):$InputPins Delay(ns) Slack(ns) Pins 9.17 N/A From: DFN1C1_Q_9_inst:CLK To: DFN1C1_Q_31_inst:D Set Register to Register From: DFN1C1_Q_9_inst:CLK To: DFN1C1_Q_31_inst:D Delay (ns): 9.17 Slack (ns): 40.301 Arrival (ns): 13.133 Required (ns): 53.434 Setup (ns): 0.539 Minimum Period (ns): 9.709

21. Additional details are available (expanded path) in the new timing report Clock Domain: Clock Expanded Path 1 From: DFN1C1_Q_9_inst:CLK To: DFN1C1_Q_31_inst:D data required time 53.434 data arrival time - 13.133 slack 40.301 ________________________________________________________ Data arrival time calculation 0.000 Clock + 3.973 clock network 3.973 DFN1C1_Q_9_inst:CLK (r) + 0.568 cell: ADLIB:DFN1C1 4.541 DFN1C1_Q_9_inst:Q (r) + 1.478 net: q_9_net_c ... ... ... 12.821 XOR2_Sum_31_inst:Y (f) + 0.312 net: sum_31_net 13.133 DFN1C1_Q_31_inst:D (f) 13.133 data arrival time ________________________________________________________ Data required time calculation 50.000 Clock + 3.973 clock network 53.973 DFN1C1_Q_31_inst:CLK (r) - 0.539 Library setup: ADLIB:DFN1C1 53.434 DFN1C1_Q_31_inst:D 53.434 data required time Timing Report Summary (cont’d)