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Recent content by mwb

  1. M

    DC Optimize Registers message

    Hi, Im getting used to using "optimize_registers" in dc for retiming, everything that I'm doing seems to be working. However, I do get this output message during the optimization: Warning: The output port 'CTL_SP[28]' has output rise and fall delay that is smaller than the estimated...
  2. M

    Design Compiler Register Retiming and CDC

    Re: Design Compiler Register Retiming and Synchronization Thanks. Seems obvious now that I think about it, worked.
  3. M

    Design Compiler Register Retiming and CDC

    Design Compiler Register Retiming and Synchronization Hi, I'm using the following command to retime a design in DC: optimize_registers -sync_transform decompose -async_transform decompose I now need to change my design in such a way that adds synchronizers for 2 inputs. How can I tell DC not...
  4. M

    Synchronous Reset and Load STA and SR feedback

    Attached below is a simplified schematic showing the circuit and feedback. Also shown is a simplified diagram of how and why Im sending the reset through a synchronizer even though the DFF's are synchronous reset. The "load" signal loads "load_val" into the shift register via a selector mux and...
  5. M

    When can we avoid using reset synchronizer?

    How else can you guarantee that just after power-up the registers are in a known state? I guess if you use some pull-ups/downs you can do it but thats probably not the best design practice.
  6. M

    Synchronous Reset and Load STA and SR feedback

    I have synthesized a shift-register with feedback and adjustable feedback taps. I have two questions: 1) The SR has a load and a reset, both synchronous. Both load and reset signals come from off-chip and are not synchronous to the clk so I have sent them both through FIFO synchronizers. My...
  7. M

    Implication of not specifying input delay constraint

    Its not by much, ~20ps, I guess Im splitting hairs but yes, its better for the smaller designs. The wireload model is the standard model that comes with the PDK, in this case, TSMC65. What I meant by "more accurate" is that the P+R tool takes into account wire length. Im not too worried...
  8. M

    clock tree sysnthesis

    Re: clocktree sysnthesis Hey pal, encounter will even create the clock tree synthesis file for you, just click around.....
  9. M

    Implication of not specifying input delay constraint

    OK, let me address #1: The test setup consists of an FPGA that is sending the data to the ASIC's internal shift register. I can constrain the FPGA to output the data on the rising clock edge. The in2reg setup and hold time slacks are 1ns and 750ps respectively so I really doubt there will be a...
  10. M

    Implication of not specifying input delay constraint

    Yea, thanks. Got it. I rechecked all my timing reports and it looks like delay=0 is the default, but reassurance would be good.
  11. M

    Implication of not specifying input delay constraint

    Ok, maybe I didn't explain it right. FPGA -> ASIC (with shift register inside) The FPGA will output the serial data aligned to the rising clock edge. The ASIC, which I gave the timing constraints for in the original post, will shift in the data and then latch out a parallel stream. The ASIC...
  12. M

    DRC Violations in Encounter

    How are you checking the DRC errors? You can output a list that shows what kinds of DRC violations. Do that and post it here. Its under "verify geometry".
  13. M

    Implication of not specifying input delay constraint

    I have a serial-to-parallel converter based on a shift register and a bank of flip-flops that latches the data out. My timing constraint file is below. Clk is the serial clock and p_clk controls the output dffs. set_wire_load_model -name "TSMC8K_Lowk_Aggresive" set_wire_load_mode top...
  14. M

    [moved] Shift Register and Serial-In Parallel Out converter

    Im taping out a chip that requires a robust serial-to-parallel converter. What is posted below seems to synthesize correctly but I have the following questions: I use asynchronous resets because there are two clocks, p_clk and clk. clk shifts in the serial data, p_clk latches it out. Async...
  15. M

    Vector Modulator vs VGA+Phase shifter

    Are there any major tradeoffs between using a vector modulator or a VGA+phase shifter in a phased array? I'm thinking frequency of operation, ie, I haven't seen many VGA architectures for >5 GHz. Otherwise, there is no major difference other than the circuits themselves, you either change phase...

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