7761 - Why is the output of "des_set_operating_condition" is always -1C in TCL+?
Below is a step-by-step explanation on why the default operating temperature in TCL+ defaults to -1C and observe its effect on timing analysis:
1. When you open the PAR-generated UDB file using des_read_udb and run des_report_operating_condition, the reported temperature is typically shown as -1C
% des_report_operating_condition
Operation: Industrial
Temperature: -1C
Speed grade: 9_High-Performance_1.0V
This -1C is only a placeholder indicating that the tool is using the default temperature defined in the PDC file or Device Constraint Editor, not an actual -1°C setting. The timing analysis tool will still use the temperature setting that you have set on your PDC file or in the Device Constraint Editor unless you change the temperature via "des_set_operating_condition" command.
2. When a user executes:
% des_set_operating_condition -temp 100
The console may indicate that the temperature is already set, and des_report_operating_condition will still show -1C afterwards.
This is because the tool continues to use the default value (e.g., 100C) defined elsewhere.
3. When a new temperature is explicitly set (e.g., -40C), the placeholder -1C is replaced:
% des_set_operating_condition -temp -40
Changing speed to 9_High-Performance_1.0V; changing temperature to -40
% des_report_operating_condition
Temperature: -40C
4. Once the default is overridden, any new temperature setting will be reflected directly:
% des_set_operating_condition -temp 100
Changing speed to 9_High-Performance_1.0V; changing temperature to 100
% des_report_operating_condition
Temperature: 100C
If you do timing analysis after setting the operating condition, you should be able to see the timing results difference
The timing tool will also mention that the operating condition you set is only used for the Timing Analysis result in the TCL console
Here's an example:
1. Report the operating condition:
% des_report_operating_condition
Operation: Industrial
Temperature: -1C
Speed grade: 9_High-Performance_1.0V
Note: the default temperature I set is 50C
2. Do timing analysis with -1C output from #1:
% sta_report_timing
Worst derating enable is 0
Synchronizing changes
Initializing timer
Starting design annotation....
INFO: user temperature only will be used in analysis
INFO: user temperature only will be used in analysis
Starting full timing analysis...
++++ Path 1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Path Begin : led_pad[5].bb_inst_IOL/DOUT (SIOLOGIC_CORE_IOL_R24A)
Path End : led[5] (certuspro_nx_kit)
Source Clock : clk_12mhz (R)
Destination Clock: clk_12mhz (R)
Logic Level : 2
Delay Ratio : 1.8% (route), 98.2% (logic)
Clock Skew : -3.921 ns
Setup Constraint : 83.333 ns
Common Path Skew : 0.000 ns
Path Slack : 0.975 ns (Passed)
3. Now, change the temperature to -40C:
% des_set_operating_condition -temp -40
Changing speed to 9_High-Performance_1.0V; changing temperature to -40
4. Run timing analysis again, and you can see the difference in results:
% sta_report_timing
++++ Path 1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Path Begin : led_pad[5].bb_inst_IOL/DOUT (SIOLOGIC_CORE_IOL_R24A)
Path End : led[5] (certuspro_nx_kit)
Source Clock : clk_12mhz (R)
Destination Clock: clk_12mhz (R)
Logic Level : 2
Delay Ratio : 2.0% (route), 98.0% (logic)
Clock Skew : -4.021 ns
Setup Constraint : 83.333 ns
Common Path Skew : 0.000 ns
Path Slack : 0.798 ns (Passed)
5. Change the temperature back to the default 50C and you can see that the result is similar to Step #2 which is "-1C"
% des_set_operating_condition -temp 50
Changing speed to 9_High-Performance_1.0V; changing temperature to 50
0
% sta_report_timing
++++ Path 1 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Path Begin : led_pad[5].bb_inst_IOL/DOUT (SIOLOGIC_CORE_IOL_R24A)
Path End : led[5] (certuspro_nx_kit)
Source Clock : clk_12mhz (R)
Destination Clock: clk_12mhz (R)
Logic Level : 2
Delay Ratio : 1.8% (route), 98.2% (logic)
Clock Skew : -3.921 ns
Setup Constraint : 83.333 ns
Common Path Skew : 0.000 ns
Path Slack : 0.975 ns (Passed)
Example Comparison:
- Default (50C via PDC, but shown as -1C):
- Path Slack: 0.975 ns
- After setting to -40C:
- Path Slack: 0.798 ns
- Reverting to 50C:
- Path Slack: 0.975 ns
This confirms that the tool correctly applies the user-defined temperature during timing analysis, even if -1C is displayed in the operating condition report.
Related Articles
7766 - iCEcube2 Modelsim: How do I run Timing simulation for iCECube2 Devices?
In order to ran through Timing simulation for iCECube2 Devices, You would need the following Libraries: 1) sb_ice_ipenc_modelsim.v [Optional: Add this if Hardened IPs are present in your design, Example: SPI, i2C] 2) sb_ice_lc.v 3) sb_ice_syn.v 4) ...7143 - Radiant: How to save design phase report files via TCL scripting each time the design is recompiled?
There is no specific command to retain the log files every time you recompile each design phase. As a workaround, the user can use the "file copy" tcl command after each design phase to copy the logs to a different folder from each design phase and ...6826 - Radiant: What type of clocks do the Clock Port column of the I/O Timing Analysis Report refer to?
For I/O timing analysis, the "Clock Port" column/field could refer to the following depending on the destination clock: 1. Internal oscillator clock: If the destination clock is directly from the internal oscillator, or if the destination clock is ...2592 - What does "potential circuit loops found in timing analysis" in trace report mean?
Solution: The use of combinational loops has long been discouraged because this can cause significant stability and reliability problems in a design. The combinational loop behavior is usually dependent on the relative propagation delays of the ...740 - Lattice ispLEVER: Timing Analysis: What is the I/O Timing Report?
Lattice ispLEVER: Timing Analysis: The I/O Timing Report (.ior) is a used to report the IO timing analysis of your design. Input Setup and Hold times (Tsu, Th) and Clock-to-Output times (Tco) are reported. The IO Timing Report sweeps across all the ...