max80_fw/fpga/max80.sdc

# -*- tcl -*-

# Clock constraints

# Input master clock for all PLLs
create_clock -name "clock_48" -period 20.834ns [get_ports {clock_48}]
derive_pll_clocks

# Handle both the RTC input clock and the internal workaround
# The internal workaround clock should still be treated an asynchronous
create_clock -name "rtc_32khz" -period 30517.578ns [get_ports {rtc_32khz}]
create_clock -name "ctr_32khz" -period 30517.578ns [get_registers {ctr_32khz}]
set_clock_groups -asynchronous -group {rtc_32khz}
set_clock_groups -asynchronous -group {ctr_32khz}

# Automatically calculate clock uncertainty to jitter and other effects.
derive_clock_uncertainty

# Don't report signaltap clock problems...
set_false_path -to [get_registers sld_signaltap:*]

# -------- PLL clock mappings --------

set sdram_out_clk [get_clocks {pll|*|clk[0]}]
set sdram_clk     [get_clocks {pll|*|clk[4]}]
set sys_clk       [get_clocks {pll|*|clk[1]}]
set vid_clk       [get_clocks {pll|*|clk[2]}]
set flash_clk     [get_clocks {pll|*|clk[3]}]

set main_clocks   [get_clocks {pll|*}]

# Reset isn't actually a clock, but Quartus thinks it is
create_generated_clock -name rst_n \
    -source [get_nets {pll|*|*clk[1]}] \
    [get_registers rst_n]

# Reset is asynchronous  with everything as far as we are concerned.
set_clock_groups -asynchronous \
    -group $main_clocks \
    -group [get_clocks rst_n]

# Anything that feeds into a synchronizer is by definition
# asynchronous, but encode it as allowing multicycle of one
# clock, to limit the possible skew (but it is of course not possible
# to eliminate it...)
set synchro_inputs [get_registers *|synchronizer:*|qreg0*] 
set_multicycle_path -from [all_clocks] -to $synchro_inputs \
    -start -setup 2
set_multicycle_path -from [all_clocks] -to $synchro_inputs \
    -start -hold 1


# -------- SDRAM I/O constraints --------

set sr_data_out [remove_from_collection [get_ports sr_*] sr_clk]
set sr_data_in  [get_ports sr_dq\[*\]]
set_max_skew -to $sr_data_out 0.100ns
set_input_delay  -clock $sdram_clk 0.500ns  $sr_data_in

set_multicycle_path -from $sdram_clk -to $sdram_out_clk \
    -start -setup 2
set_multicycle_path -from $sdram_clk -to $sdram_out_clk \
    -start -hold 0

# -------- SPI ROM multicycle paths --------

# the load of the spi_data_ctr register happens no less than 2 target
# clocks after datalen is loaded by the CPU
set_multicycle_path -from [get_registers {spirom:*|datalen[*]}] \
    -to [get_registers {spirom:*|spi_data_ctr[*]}] -end -setup 2
set_multicycle_path -from [get_registers {spirom:*|datalen[*]}] \
    -to [get_registers {spirom:*|spi_data_ctr[*]}] -end -hold 1

# A load of romstart does not affect spi_cmd for a minimum of 3 target
# clock cycles (in reality much more, since the CPU needs to
# write datalen in order to start the transfer)
set_multicycle_path -from [get_registers {spirom:*|romstart[*]}] \
    -to [get_registers {spirom:*|spi_cmd[*]}] -end -setup 3
set_multicycle_path -from [get_registers {spirom:*|romstart[*]}] \
    -to [get_registers {spirom:*|spi_cmd[*]}] -end -hold 2

# CS# going low to spi_clk_en is a minimum of one clock cycle, which allows
# an extra clock cycle before spi_cmd needs to stop resetting
set_multicycle_path -from [get_registers {spirom:*|spi_cs_n}] \
    -to [get_registers {spirom:*|spi_cmd[*]}] -end -setup 2
set_multicycle_path -from [get_registers {spirom:*|spi_cs_n}] \
    -to [get_registers {spirom:*|spi_cmd[*]}] -end -hold 1

# -------- CPU/fastmem multicycle paths --------

# We never read and write in the same clock cycle, thus there is a multicycle
# path from the write enable register to anything in the CPU itself
set_multicycle_path -from [get_keepers {fast_mem:fast_mem|*porta_we_reg*}] \
    -to [get_keepers {picorv32:cpu|*}] -start -setup 2
set_multicycle_path -from [get_keepers {fast_mem:fast_mem|*porta_we_reg*}] \
    -to [get_keepers {picorv32:cpu|*}] -start -hold 1