Synopsys Design Compiler-A quick Tutorial

From: http://www.vlsiip.com/dc_shell/

Step 0. Invoke Design Compiler
unix> dc_shell-t
Step 1. Setup technology library. To synthesize a design you need technology library which will contain
description of the cells from the fab, and their timing. This is usually a .db file found in
library installation directory. To do this
1(a). Tell synopsys where your <library>.db file is.
set search_path {/homes/amittal/s5/work/physical_lib/corelib/tsmc_090_g_art}
1(b). Tell synopsys what is your technology library, which you want to map your design on called
set target_library {scadv_tsmc_cln90g_lvt_ss_0p9v_125c.db}
1(c). Set up link libraries. This is optional .db files which are pre synthesized and ready to be read in
For this, append your search path where your optional .db files are
lappend search_path {[exec pwd]}
lappend search_path {.}
1(d). Set up link libraries. This is optional .db files which are pre synthesized and ready to be read in
set link_library {PLL10CCMID_W_125_1.35.db}
Step 2. Read In your design files
2(a). if it is verilog:
read_verilog counter.v
2(b). if it is vhdl: As it is in this tutorial
read_vhdl counter.vhd
read_vhdl counter_top.vhd
2(c). if it is ddc:
read_ddc counter.ddc
Step 3. Set Design Constraints:
3(a) Set frequency of operation: You have to create a clock in the design,
With a given timeperiod. The command below creates a clock and calls it
'design_clk' with a timeperiod of 10 ns, (100MHz), and maps it to the
'clk' input of the design.
create_clock -period 10 -name design_clk clk
3(b) Set input constraints : Set how much time would be spent by
signals arriving into your design, outside your design with respect to the clock
set_input_delay 4.0 [remove_from_collection [all_inputs ] clk] -clock design_clk
3(c) Set output constraints : Set how much time would be spent by
signals leaving your desing, outside your design, before they are captured by
the same clock
set_output_delay 7.0 [all_outputs] -clock design_clk
3(d) Set area constraints : set maximum allowed area to 0 :). well its just to
instruct design compiler that use as less area as possible.
set_max_area 0
Step 4. Enable clock gating for low power (optional)
4(a) The following commands will try to insert clock gates for each 2 registers
set_clock_gating_style -minimum_bitwidth 2
Step 5. Write formal verification setupfile (optional)
set_svf -append "counter.svf"
Step 6. Set Register optimization veriables (optional)
(a) Set automatic removal of constant flipflop(s)
set compile_seqmap_propagate_constants true
(b) Set automatic removal of unloaded flipflop(s)
set compile_delete_unloaded_sequential_cells false
Step 7. Set mapping of sync resets to aviod Xs in sims (optional)
set hdlin_ff_always_sync_set_reset "true"
Step 8. Set the name of top level as current design and compile the design
(a) current_design counter_top
compile -map_effort high
(b) If you are using dc ultra :
compile_ultra
You may want to turn off output inversion of sequential cells
compile_ultra -no_seq_output_inversion
Step 9. Write design output netlist
9(a).Write output in ddc format
write -format ddc -output counter.ddc -hier
9(b).Write output in verilog format
write -format ddc -output counter.vlog -hier
Step 10. You may want to flatten your design before writing out netlist
ungroup -all -flatten
write -format verilog -output counter_flat.vlog
Step 11. Writing a timing report of your design
report_timing > counter_timing.rep
Step 12. Quit Design Compiler
quit

More random DC shell Tcl mode Commands:

define_design_lib lib1 -path ~/misc/vhdl
analyze -library lib1 -format vhdl /homes/amittal/misc/vhdl/xx.vhdl
get_design_lib_path SYNTH
get_design_lib_path work

read_verilog mse.v

report_timing -delay max -from ARRAYCACHE_I/CACHEDIRRAM_I/regfile64x704_assembly_0/RA_ram[3] -to pCacheMemReqFifoDataOut

report_timing -delay max -through [find net ARRAYCACHE_I/CACHEDIRRAM_I/regfile64x704_assembly_0/RA_ram[3]]

report_constraint -verbose -all_violators

create_clock -name "myclk" -period 13 [get_ports pClk]

set_output_delay 1.0 -clock [get_clocks myclk] pCacheMemReqFifoDataOut[161]

set_wire_load_mode segmented

set_wire_load_mode enclosed

update_timing

report_timing -from [find pin ARRAYCACHE_I/LatencyReqReg*/Q] -to pCacheMemReqFifoDataOut

report_timing -from [find pin ARRAYCACHE_I/CACHE_DATA_RAM/DO*] -to pCacheMemReqFifoDataOut

set_output_delay 1.0 -clock myclk pCacheMemReqFifoDataOut

set_false_path -through [find pin ARRAYCACHE_I/FracSetReg*/*]index

It is to be noted that if there are no constraints, 'set_false_path' does not actually works.

I tried to find delays to a output port, without any constraints, form a known point in the design.
I got that.
Then I wanted to find next worst path to that output port, to I set a false path on the path found above.
But it wouldn't work
I then created a clcok and constrainted the output port,
!! False path worked.... magic :)

create_clock -period 4.8 -name vclk
set_input_delay 2.5 pDmaReadRegIndex -clock vclk -add_delay
set_output_delay 2.5 pInsertNopOut -clock vclk -add_delay
set_false_path -from vclk -to PESWITCH_pClk
set_false_path -from PESWITCH_pClk -to vclk
set_false_path -from PESWITCH_pClk -through pDmaReadRegIndex -to pInsertNopOut
report_timing -from pDmaReadRegIndex -to pInsertNopOut

set_input_delay [expr 0.35*$vclk_period] [all_inputs] -clock vclk -add_delay
set_output_delay [expr 0.35*$vclk_period] [all_outputs] -clock vclk -add_delay
set_false_path -from PESWITCH_pClk -through [all_inputs] -to [all_outputs]


set compile_log_format "%elap_time %area %wns %tns %drc %endpoint %group_path"