| ??? 12/06/09 06:24 Read: times Msg Score: +1 +1 Good Answer/Helpful |
#171483 - Simple Solutions Exist Responding to: ???'s previous message |
I did not see any specific timing requirements in your post, so here are my ideas. If you simply need to expand the "output" pins available, a simple serial-in, parallel-out (SIPO) circuit will allow 8 or more pins from 3 pins (or 2, with a little trickery & slightly slower) using SIPO logic ICs like the 74HC595. If you need higher speed, parallel I/Os, then perhaps you should use classic latching/buffered circuits were data is latched out onto an 8-bit bus, relieving the source port to use the 8 I/Os for other purposes. For the Tx & Rx pins, assuming the operation scenario allows for it, I would use a select line and AND or NAND based logic to easily select the Tx/Rx pair. Are these strictly output or input AND output functions for the pins in question? Recently I had a new design which required 8 additional pins; I used the SIPO scheme to get 8 OUTPUT pins from 3 microcontroller pins. Here, speed was not a design goal...but the software function was VERY easy! I would strongly encourage you to rely on simple hardware solutions (vs. a programmable solution) unless there are design goals for your project. ..or if you could clarify EXACTLY what your needs are, that would be helpful... |
| Topic | Author | Date |
| CPLD or µc? | 01/01/70 00:00 | |
| Whatever you are comfortable with | 01/01/70 00:00 | |
| Expanding I/O | 01/01/70 00:00 | |
| the other route ... | 01/01/70 00:00 | |
| Thanks | 01/01/70 00:00 | |
| how 'hard' is the choice ? | 01/01/70 00:00 | |
Simple Solutions Exist | 01/01/70 00:00 |