| ??? 09/21/11 01:52 Modified: 09/21/11 01:53 Read: times |
#183818 - These aren't necessarily so "huge" Responding to: ???'s previous message |
Per Westermark said:
I think I will try to go the route of promoting adapter boards, with each ribbon cable being replaced with two or four inputs and same number of outputs and the other end extracting into 8 in/8 out or whatever that specific device may require.
That would decouple choice of voltages, selection of series resistances, pull-up resistors, EMI-filters, ... from the control electronics, while reducing problems with end-of-life for critical components, basically making the main processor the only really critical component. "Owning" both sides of the cable means that the cable signals can use optimal drive strength etc, before switching to correct voltage levels, current drive etc. Of course, I'm not into the position to make such a decision. But it should be a presentable solution that does have advantages not covered by a single, huge, FPGA. I doubt you'd consider a CPLD in a TQFP-80 or -100 package to be that "huge" nor are they particularly costly or difficult to use. Some FPGA's come in pretty small packages as well, though they tend to be BGA's, which have their own pitfalls. Because you can generally pick your own pinout, within certain limits, you might actually find a relatively inexpensive programmable part to simplify things for you, including the layout. Some of those older FPGA's to which I referred, however, also provide internal pullups and other types of termination, and allow you to choose different I/O voltages for different I/O blocks. You might find that convenient as well. Take a look ... I believe you'll find a happy solution. RE |
