Below is a sample SDC file for a design with DDR memory. This file will typically include:
- Clock constraints: Define the clocks for the DDR interface.
- Input/Output delay constraints: Specify timing for the DDR I/O signals.
- Pin constraints: Assign pins for the DDR signals.
- Timing constraints: Define the setup and hold times, etc., for DDR.
Example SDC file for DDR memory
# Set the main clock period
set_clock_period -period 5.0 [get_clocks ddr_clk] # DDR clock period (200 MHz)
# Define the DDR interface clock
create_clock -period 5.0 -name ddr_clk -waveform {0 2.5} [get_pins ddr_clk] # Create a clock for the DDR interface
# Define input and output delays
set_input_delay -max 2.0 -min 1.5 -clock [get_clocks ddr_clk] [get_pins ddr_dq] # Input delay for DDR DQ
set_output_delay -max 2.0 -min 1.5 -clock [get_clocks ddr_clk] [get_pins ddr_dq] # Output delay for DDR DQ
# Set the input delay for address and control signals
set_input_delay -max 1.5 -min 1.0 -clock [get_clocks ddr_clk] [get_pins ddr_addr] # Address input delay
set_input_delay -max 1.5 -min 1.0 -clock [get_clocks ddr_clk] [get_pins ddr_cmd] # Command input delay
# Set the I/O delays for the DDR data signals (DQ) and DDR command/address signals (CS, WE, etc.)
set_input_delay -max 2.0 -min 1.0 -clock [get_clocks ddr_clk] [get_pins ddr_dq]
set_output_delay -max 2.0 -min 1.0 -clock [get_clocks ddr_clk] [get_pins ddr_dq]
# Define setup and hold constraints for the DDR signals (timing checks)
set_multicycle_path -setup 2 -hold 1 [get_clocks ddr_clk] # Setup and hold for DDR clock
# Define constraints for the DDR address bus (address lines)
set_input_delay -max 1.0 -min 0.5 -clock [get_clocks ddr_clk] [get_pins ddr_addr]
# Define the timing requirements for DDR commands (CS, RAS, CAS, WE)
set_input_delay -max 1.5 -min 1.0 -clock [get_clocks ddr_clk] [get_pins ddr_cmd]
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