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Adventurer
Adventurer
121 Views
Registered: ‎01-02-2012

Making route_design to do more iterations in order to meet -min_delay & -max_delay limits

Hi experts!

help route_design 

did not help much. When pre routing a few critical paths (all routing resources being free), is it possible to make route_design to do more iterations in order to meet -min_delay & -max_delay limits? 

It runs fast and does not seem to be trying hard at all:

route_design -pins [get_pins [list {ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_*/D}   \
                                   {ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rx_c*/D}   \
                   ]] -min_delay 2800 -max_delay 3400
...
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rx_ctl_f_reg_reg/D', mapped to sitepin 'SLICE_X85Y110/A6'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rx_ctl_r_reg_reg/D', mapped to sitepin 'SLICE_X84Y111/A6'
WARNING: [Route 35-347] Router failed to meet '-max_delay' requirement of 3400ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[0]/D', mapped to sitepin 'SLICE_X84Y111/BX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[0]/D', mapped to sitepin 'SLICE_X84Y111/BX'
WARNING: [Route 35-347] Router failed to meet '-max_delay' requirement of 3400ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[1]/D', mapped to sitepin 'SLICE_X84Y111/CX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[1]/D', mapped to sitepin 'SLICE_X84Y111/CX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[2]/D', mapped to sitepin 'SLICE_X84Y111/DX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[3]/D', mapped to sitepin 'SLICE_X84Y111/AX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[4]/D', mapped to sitepin 'SLICE_X85Y110/BX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[5]/D', mapped to sitepin 'SLICE_X85Y110/CX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[6]/D', mapped to sitepin 'SLICE_X85Y110/DX'
WARNING: [Route 35-348] Router failed to meet '-min_delay' requirement of 2800ps on pin 'ob_mac_inst/gmii2rgmii_wrap_inst/gmii2rgmii_inst/rx_regs.gmii_rxd_reg_reg[7]/D', mapped to sitepin 'SLICE_X85Y110/AX'

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Historian
Historian
99 Views
Registered: ‎01-23-2009

Re: Making route_design to do more iterations in order to meet -min_delay & -max_delay limits

Your requirements are likely impossible to meet.

I don't know exactly how the min_delay and max_delay options work, but if they are "across all PVT corners" then they are impossible. Routing delay is dominated by the interconnect delay, which is transistor based. All transistors vary in performance across Process/Voltage/Temperature (PVT). The rule of thumb is around 3:1. So if you ask for a min_delay of 2800, then the best max_delay you are likely to be able to attain is around 8400.

And why are you trying to do this? Controlling the router at this level is never required for "normal" designs, and from the name, this looks like regular logic. Why do you think you need to try and constrain the router this way?

Avrum