Hi, I want to generate metastability-based true random numbers using a model where 256 R - S latches are connected in parallel, as in Figure 1. For this, I have to place the NAND gates that make up each R-S latch core in Figure 2 on a different LE on the FPGA (chipplanner). However, the modeled system is optimized by Quartus at the compilation stage and placed on LEs in a stochastic way. Although I tried hard, I could not get a result. I need your knowledge and experience to solve this problem, which is important to me. For this I need to make any adjustments in the Quartus environment or what method should I follow?
I would be very happy if you could help me.
Figure 1. Entropy model
Figure 2. SR latch
Hi agaripcan6223 !
In order to create such a design you need to exploit hand placing the LUTs.
Have you tried using Assignments - Location -> LAB combinational cell?
Other issue is to create LUT mask to behave as NAND gate - you need to create hand placed LUTs and change their LUT mask using Resource property editor.
I also need to say that your design is highly unrecommended in FPGAs, here you create clock gating and combinational loops.
You can prevent optimization by setting the preserve synthesis attribute on the register. You may refer to the syntax below.