Visible to Intel only — GUID: uyv1663048819972
Ixiasoft
Visible to Intel only — GUID: uyv1663048819972
Ixiasoft
3.2.5.2. Maximum Allowable External nCSO Pin Skew Delay Guidelines
Use the following equations to determine the skew between nCSO and AS_CLK:
- Skew (Tbd_clk – Tbd_ncso) > Tsu_ncso – Tdcsfrs
- Skew (Tbd_clk – Tbd_ncso) < AS_CLK/2 + Tdcslst – Tho_ncso
Hence, the allowable range for skew between nCSO and AS_CLK is as follows:
Tsu_ncso - Tdcsfrs < Skew (Tbd_clk – Tbd_ncso) < AS_CLK/2 + Tdcslst - Tho_ncso
- Tsu_ncso = Chip select setup time required by the quad SPI flash. Refer to your quad SPI flash datasheet.
- Tho_ncso = Chip select hold time required by the quad SPI flash. Refer to your quad SPI flash datasheet.
- Tdcsfrs = AS_nCSO[3:0] asserted to first AS_CLK edge. Refer to the AS configuration timing specifications in the Stratix® 10 Device Data Sheet.
- Tdcslst = Last AS_CLK edge to AS_nCSO[3:0] deasserted. Refer to the AS configuration timing specifications in the Stratix® 10 Device Data Sheet.
- AS_CLK = AS_CLK clock period.
Example to Determine the Skew for 1 GB Quad SPI Flash Devices
Tsu_ncso = 2.7 ns
Tho_ncso = 3.375 ns
Tdcsfrs = 11.65 ns
Tdcslst = 9.23 ns
AS_CLK = 8 ns (125 MHz)
- Skew (Tbd_clk – Tbd_ncso) > Tsu_ncso – Tdcsfrs
Skew (Tbd_clk – Tbd_ncso) > 2.7 – 11.65
Skew (Tbd_clk – Tbd_ncso) > –8.95 ns
- Skew (Tbd_clk – Tbd_ncso) < AS_CLK/2 + Tdcslst – Tho_ncso
Skew (Tbd_clk – Tbd_ncso) < 8/2 + 9.23 – 3.375
Skew (Tbd_clk – Tbd_ncso) < 9.855 ns
The allowable range for skew between nCSO and AS_CLK is -8.95 ns < Skew (Tbd_clk – Tbd_ncso) < 9.855 ns