Step 9: Generating the Bitstreams - 2021.2 English

Vivado Design Suite Tutorial: Dynamic Function eXchange (UG947)
Document ID
UG947
Release Date
2022-04-18
Version
2021.2 English

Verifying the Configurations

Recommended: Before generating bitstreams, verify all configurations to ensure that the static portion of each configuration match identically, so the resulting bitstreams are safe to use in silicon. The PR Verify feature examines the complete static design up to and including the partition pins, confirming that they are identical. Placement and routing within the Reconfigurable Modules is not checked, as different module results are expected here.
  1. Run the pr_verify command from the Tcl Console:
    pr_verify Implement/Config_shift_right_count_up_implement/top_route_design.dcp 
Implement/Config_shift_left_count_down_import/top_route_design.dcp

    If successful, this command returns the following message.INFO: [Vivado 12-3253] PR_VERIFY: check points Implement/Config_shift_right_count_up/top_route_design.dcp and Implement/Config_shift_left_count_down/top_route_design.dcp are compatible

    By default, only the first mismatch (if any) is reported. To see all mismatches, use the -full_check option.

  2. Close the project:
    close_project

Generating Bitstreams

Now that the configurations have been verified, you can generate bitstreams and use them to target your selected demonstration board.

Note: The first configuration implements shift_right and count_up. The second configuration implements shift_left and count_down.
  1. Read the first configuration into memory:
    open_checkpoint Implement/Config_shift_right_count_up_implement/top_route_design.dcp
  2. Generate full and partial bitstreams for this design. Be sure to keep the bit files in a unique directory related to the full design checkpoint from which they were created. 
    write_bitstream -force -file Bitstreams/Config_RightUp.bit 
close_project
    Notice that five (or three, if you are using an UltraScale+™ device) bitstreams have been created:
    • Config_RightUp.bit This is the power-up, full design bitstream. The four shift LEDs on the right will shift right and the four count LEDs on the left will count up.
    • Config_RightUp_pblock_inst_shift_partial.bit This is the partial bit file for the shift_right module that causes the shift LEDs to shift right.
    • Config_RightUp_pblock_inst_count_partial.bit This is the partial bit file for the count_up module that causes the count LEDs to count up.
    • Config_RightUp_pblock_inst_shift_partial_clear.bit This is the clearing bit file for the shift_right module for UltraScale devices only. It safely clears a right shift to allow the shift module to be reconfigured.
    • Config_RightUp_pblock_inst_count_partial_clear.bit This is the clearing bit file for the count_up module for UltraScale devices only. It safely clears an up count to allow the count module to be reconfigured.
Important: When generated by a single call to write_bitstream, the names of the bit files currently do not reflect the name of the Reconfigurable Module variant to clarify which image is loaded. The current solution uses the base name given by the - file option and appends the Pblock name of the reconfigurable cell. It is critical to provide enough description in the base name to be able to identify the reconfigurable bit files clearly. All partial bit files have the _partial postfix, and all clearing bit files have the _partial_clear postfix.
Using run_dfx.tcl to process the entire design through bitstream generation, uses a different technique for generating the bitstreams. Opening a routed design checkpoint issues multiple calls to write_bitstream, which gives you more control over naming bitstreams and allows for different options (such a bitstream compression) to be applied to full versus partial bitstreams. For example, the names configured in the run_dfx.tcl script are:
  • Config_shift_right_count_up_implement_full.bit This is the power-up, full design bitstream.
  • pblock_shift_shift_right_partial.bit This is the partial bit file for the shift_right module.
  • pblock_count_count_up_partial.bit This is the partial bit file for the count_up module.
  • pblock_shift_shift_right_partial_clear.bit This is the clearing bit file for the shift_right module for UltraScale devices only.
  • pblock_count_count_up_partial_clear.bit This is the clearing bit file for the count_up module for UltraScale devices only.
  1. Generate full and partial bitstreams for the second configuration, again keeping the resulting bit files in the appropriate folder.
    open_checkpoint Implement/Config_shift_left_count_down_import/top_route_design.dcp
write_bitstream -force -file Bitstreams/Config_LeftDown.bit
close_project
    Similarly, five (or three) bitstreams are created, this time with a different base name.
  2. Generate a full bitstream with grey boxes, plus blanking bitstreams for the Reconfigurable Modules. Blanking bitstreams can be used to “erase” an existing configuration to reduce power consumption.
    Note: Note: Grey box blanking bitstreams are not the same as clearing bitstreams. Clearing bitstreams are required to prepare the global signal mask for the next partial bitstream, ensuring the GSR event occurs properly.
    open_checkpoint Checkpoint/static_route_design.dcp 
update_design -cell inst_count -buffer_ports 
update_design -cell inst_shift -buffer_ports 
place_design 
route_design 
write_checkpoint -force Checkpoint/config_grey_box.dcp 
write_bitstream -force -file Bitstreams/config_grey_box.bit 
close_project
    The base configuration bitstream has no logic for either reconfigurable partition. The update_design commands here insert constant drivers (ground) for all outputs of the Reconfigurable Partitions, so these outputs do not float. The term grey box indicates that the modules are not completely empty with these LUTs inserted, as opposed to black boxes, which would have dangling nets in and out of this region. The place_design and route_design commands ensure they are completely implemented. As valid Reconfigurable Modules, note that these instances also have clearing bitstreams for UltraScale devices only.