Visible to Intel only — GUID: sss1411979414512
Ixiasoft
Visible to Intel only — GUID: sss1411979414512
Ixiasoft
1.4.2.3. Constraining Asynchronous Input and Output Ports, and Bidirectional Synchronous Ports
As for asynchronous output ports, the signals can be excluded from the timing analysis because the signals have functionally sufficient timing margin, except flash_nce and flash_addr.
For bidirectional synchronous ports, the flash access during write mode can be excluded because of sufficient timing margin, but not during read mode.
To exclude asynchronous input and output ports from the timing analysis, use the set_false_path command to ignore these ports during timing analysis.
The signal delay from PFL asynchronous output ports to flash memory device (flash_nce, flash_addr) and vice versa (flash_data in read mode) are specified by set_max_delay. The delay calculation is:
Max delay value = Distributed timing budget - board delay
Flash Access Mode | Delay Calculation |
---|---|
Normal Mode | Timing budget = [roundup(Taccess_pfl/Tpfl_clk) + 1] * Tpfl_clk - Taccess Distribute the timing budget for output and input delay: Output delay (flash_addr, flash_nce) =Timing budget (major) – board delay from PFL to flash Input delay (flash_data) = Timing budget (minor) - board delay from flash to PFL |
Page Mode | Timing budget = [roundup(Tpage_access_pfl/Tpfl_clk) + 1]* Tpfl_clk- Tpage_access Distribute the timing budget for output and input delay: Output delay (flash_addr, flash_nce) = Timing budget (major) - board delay from PFL to flash Input delay (flash_data) = Timing budget (minor) - board delay from flash to PFL Note: Evaluate timing using both Taccess and Tpage_access and select the tighter constraint. |
- Taccess_pfl is the flash access time. Refer Table PFL FPGA Configuration Parameters. Tpage_access_pfl is set to 30 ns in the PFL IP core.
- Taccess and Tpage_access are FLASH ROM time specification during Normal and Page access respectively.