| ??? 06/06/06 10:52 Modified: 06/06/06 12:18 Read: times |
#117850 - strictly speaking... Responding to: ???'s previous message |
Andy Neil said:
you will see that there's a maximum IOL of 10mA per pin, but an overall port limit of 26mA (Port 0) or 15mA (Ports 1-3).
There is also a maximum total for the whole chip of 71mA. These things basically boil down to power dissipation. Strictly speaking, this is limited by ohmic resistance of the common ground paths (bond + on chip interconnects); it should be well below the thermal limits of the same. Not that this changes anything on the specified maxima. Just a sidenote, the unit TTL input load is 1.6mA when driven to 0, so "legally" it's only 9 TTL inputs per port (excl. P0). Note, however, that the 74HC/HCTxx chips and virtually all modern CMOS ICs have much lower input current, so the fan-out for them is practically infinity. JW |
| Topic | Author | Date |
| Help Understanding AT89C51 Datasheet | 01/01/70 00:00 | |
| logic gain and other | 01/01/70 00:00 | |
| Should I study more? | 01/01/70 00:00 | |
| do you have any hardware knowledge | 01/01/70 00:00 | |
| No hardware knowledge | 01/01/70 00:00 | |
| what purpose? | 01/01/70 00:00 | |
| Purpose | 01/01/70 00:00 | |
| many get confused by this | 01/01/70 00:00 | |
| Got it ! | 01/01/70 00:00 | |
| per-pin, per-port, and whole-chip limits | 01/01/70 00:00 | |
| strictly speaking... | 01/01/70 00:00 | |
| Slight oversimplification | 01/01/70 00:00 | |
| it used to be DC, now it is AC | 01/01/70 00:00 | |
"per pin" | 01/01/70 00:00 | |
| Good post! | 01/01/70 00:00 | |
| Excellent Community | 01/01/70 00:00 | |
| have you read "the bible" | 01/01/70 00:00 | |
| Yes, I have started | 01/01/70 00:00 |