| ??? 11/25/07 06:30 Read: times |
#147364 - largely, it's because it's not an option Responding to: ???'s previous message |
Do you have an FPGA family that (a) is on the market, and (b) offers internal tristate resources?
Substituting multiplexers does impact timing, BTW, as one generally wouldn't consider two tristate elements on a bus, while eight or ten might not be unusual. A 1/10 mux would be a MAJOR construct, using multiple logic elements and adding LOTS of time to the propagation delay. That's one of the weaknesses in FPGA. CPLD's make muxes much easier, as they're logic-rich, though flipflop-poor, while FPGA's are flipflop-rich and logic-poor. If you need lots of wide muxes, e.g. 10 items on a 32-bit common bus, you're going to pay a price in FPGA. So far, I haven't seen a way around that. If they were to make LUT's 8-bits wide rather than 4, you could do more. However, since an FPGA is just a RAM with feedback ... RE |
| Topic | Author | Date |
| Tri-state busses in FPGAs | 01/01/70 00:00 | |
| Tristate Buffers (TBUFs) have been phased out | 01/01/70 00:00 | |
| Thank you | 01/01/70 00:00 | |
| Closing the loop | 01/01/70 00:00 | |
| siumulate? | 01/01/70 00:00 | |
| I didn't simulate it (yet) | 01/01/70 00:00 | |
| hmmm | 01/01/70 00:00 | |
| So ... what about a BIG multi-party bus? | 01/01/70 00:00 | |
| delay | 01/01/70 00:00 | |
| nevertheless ... | 01/01/70 00:00 | |
| re: nevertheless | 01/01/70 00:00 | |
| What disappoints me is the advertising vs reality | 01/01/70 00:00 | |
| advertising | 01/01/70 00:00 | |
| advertising, badvertising ... lies! | 01/01/70 00:00 | |
| oy | 01/01/70 00:00 | |
If only one could rely on them ... | 01/01/70 00:00 | |
| largely, it's because it's not an option | 01/01/70 00:00 | |
| Zackly | 01/01/70 00:00 | |
| If you have internal tristate resources ... | 01/01/70 00:00 | |
| I have new worries now | 01/01/70 00:00 | |
| tristates in FPGAs | 01/01/70 00:00 |