Startup原語及其限制
fpga掉電丢失，一般使用外部flash存儲代碼，flash有spi、bpi、qspi等接口，外部存儲器的時鐘管腳一般與fpga的CCLK_0連接配接，當使用遠端更新時，首先fpga内部有控制flash的驅動（即邏輯控制flash時序），當然flash時鐘也需要控制了，但這時時鐘管腳已經連接配接到CCLK_0，那該如何操作啊，你直接限制配置設定管腳試試，是通不過的，這時STARTUPE2就派上用場了，那該如何使用啊，如下（K7系列verilog）：
STARTUPE2 #(
.PROG_USR("FALSE"), // Activate program event security feature. Requires encrypted bitstreams.
.SIM_CCLK_FREQ(0.0) // Set the Configuration Clock Frequency(ns) for simulation
)
STARTUPE2_inst
(
.CFGCLK(), // 1-bit output: Configuration main clock output
.CFGMCLK(), // 1-bit output: Configuration internal oscillator clock output
.EOS(), // 1-bit output: Active high output signal indicating the End Of Startup.
.PREQ(), // 1-bit output: PROGRAM request to fabric output
.CLK(0), // 1-bit input: User start-up clock input
.GSR(0), // 1-bit input: Global Set/Reset input (GSR cannot be used for the port name)
.GTS(0), // 1-bit input: Global 3-state input (GTS cannot be used for the port name)
.KEYCLEARB(1), // 1-bit input: Clear AES Decrypter Key input from Battery-Backed RAM (BBRAM)
.PACK(1), // 1-bit input: PROGRAM acknowledge input
.USRCCLKO(flash_clk), // 1-bit input: User CCLK input
.USRCCLKTS(0), // 1-bit input: User CCLK 3-state enable input
.USRDONEO(1), // 1-bit input: User DONE pin output control
.USRDONETS(1) // 1-bit input: User DONE 3-state enable outpu
);
其中flash_clk就是你時序控制的flash時鐘信号，連接配接到這就行了，其它的不需要改動，也無需限制此管腳（因為此管腳不需要在頂層作為輸出信号了）。
限制如下：
set cclk_delay 6.7
# Following are the SPI device parameters
# Max Tco
set tco_max 7
# Min Tco
set tco_min 1
# Setup time requirement
set tsu 2
# Hold time requirement
set th 3
# Following are the board/trace delay numbers
# Assumption is that all Data lines are matched
set tdata_trace_delay_max 0.25
set tdata_trace_delay_min 0.25
set tclk_trace_delay_max 0.2
set tclk_trace_delay_min 0.2
### End of user provided delay numbers
# This is to ensure min routing delay from SCK generation to STARTUP input
# User should change this value based on the results
# Having more delay on this net reduces the Fmax
# Following constraint should be commented when the STARTUP block is disabled
set_max_delay 1.5 -from [get_pins -hier *SCK_O_reg_reg/C] -to [get_pins -hier *USRCCLKO] -datapath_only
set_min_delay 0.1 -from [get_pins -hier *SCK_O_reg_reg/C] -to [get_pins -hier *USRCCLKO]
# Following command creates a divide by 2 clock
# It also takes into account the delay added by the STARTUP block to route the CCLK
# This constraint is not needed when the STARTUP block is disabled
# The following constraint should be commented when the STARTUP block is disabled
create_generated_clock -name clk_sck -source [get_pins -hierarchical *axi_quad_spi_1/ext_spi_clk] [get_pins -hierarchical *USRCCLKO] -edges {3 5 7} -edge_shift [list $cclk_delay $cclk_delay $cclk_delay]
# Enable the following constraint when STARTUP block is disabled
#create_generated_clock -name clk_virt -source [get_pins -hierarchical *axi_quad_spi_1/ext_spi_clk] [get_ports <SCK_IO>] -edges {3 5 7}
# Data is captured into FPGA on the second rising edge of ext_spi_clk after the SCK falling edge
# Data is driven by the FPGA on every alternate rising_edge of ext_spi_clk
set_input_delay -clock clk_sck -max [expr $tco_max + $tdata_trace_delay_max + $tclk_trace_delay_max] [get_ports IO*_IO] -clock_fall;
set_input_delay -clock clk_sck -min [expr $tco_min + $tdata_trace_delay_min + $tclk_trace_delay_min] [get_ports IO*_IO] -clock_fall;
set_multicycle_path 2 -setup -from clk_sck -to [get_clocks -of_objects [get_pins -hierarchical */ext_spi_clk]]
set_multicycle_path 1 -hold -end -from clk_sck -to [get_clocks -of_objects [get_pins -hierarchical */ext_spi_clk]]
# Data is captured into SPI on the following rising edge of SCK
# Data is driven by the IP on alternate rising_edge of the ext_spi_clk
set_output_delay -clock clk_sck -max [expr $tsu + $tdata_trace_delay_max - $tclk_trace_delay_min] [get_ports IO*_IO];
set_output_delay -clock clk_sck -min [expr $tdata_trace_delay_min -$th - $tclk_trace_delay_max] [get_ports IO*_IO];
set_multicycle_path 2 -setup -start -from [get_clocks -of_objects [get_pins -hierarchical */ext_spi_clk]] -to clk_sck
set_multicycle_path 1 -hold -from [get_clocks -of_objects [get_pins -hierarchical */ext_spi_clk]] -to clk_sck