| ??? 01/20/06 15:28 Modified: 01/20/06 15:29 Read: times |
#107887 - Solution(?) Responding to: ???'s previous message |
I know it's late but I had an urgent problem to solve.
As Erik pointed out, the question is not unambiguous but it's not so easy to make one such. So I think the following pins are needed: VCC, GND - power supply + reference ground RxD, TxD - that was an initial requirement XTAL1 - clock input. Now this is one of the problematic places. Originally I did not think of XTAL2 as not needed, but the question allows to suppose that an external oscillator is used. So the necessary pin is only XTAL1. RESET - although some of the todays derivatives have internal reset/brownout etc. I think the original 8051 definitively needed this pin for correct start /EA - I don't have a "real" 8051, so I can't try on it, but nothing in the datasheet seems to indicate that this pin does not need to be pulled high externally for correct operation from the internal code ROM. This was in fact the original motivation for this quiz. For a hobby project I decided to use AT89C2051 (based on cost and wide availability), but for easier debugging, I used a P89V51RD2. As I am not really a hardware man, I took a couple of wires and wired it up quickly to the PCB in place of the AT89C2051... and it did not work. First I suspected the oscillator was not working (crystal and caps on PCB) due to stray capacitance/inductance of the wires, so I borrowed an oscilloscope from my work to check... but it was working. After a couple of hours spent with crazy experiments I went to see some TV and my wife, seeing I was very nervous, asked me what's wrong. While trying to explain her the problem, I realized I left the /EA pin floating... And that was it. So the correct answer is... 33. Jan Waclawek PS. I just lost the chance to get a degree at Erik's 8051 university... He personally pointed out to me the fact of /EA needs to be pulled high about a year ago... |
| Topic | Author | Date |
| Quiz of the week | 01/01/70 00:00 | |
| Eh ? | 01/01/70 00:00 | |
| how do you propose to do this,Mode0? | 01/01/70 00:00 | |
| corrected | 01/01/70 00:00 | |
| 32 | 01/01/70 00:00 | |
| this answer could be true, Jan, you shou | 01/01/70 00:00 | |
| 34 | 01/01/70 00:00 | |
| tear off | 01/01/70 00:00 | |
| if mask program | 01/01/70 00:00 | |
| Bah | 01/01/70 00:00 | |
| but you are meaner to the little bug | 01/01/70 00:00 | |
| Oops | 01/01/70 00:00 | |
| 33 | 01/01/70 00:00 | |
| 33 | 01/01/70 00:00 | |
| 32 | 01/01/70 00:00 | |
| 37 | 01/01/70 00:00 | |
| I'm dying | 01/01/70 00:00 | |
| you'll need to wait until tomorrow... | 01/01/70 00:00 | |
| and that's why I'm not postulating | 01/01/70 00:00 | |
| Power over UART ? | 01/01/70 00:00 | |
| don't guess | 01/01/70 00:00 | |
| Why not | 01/01/70 00:00 | |
| 33 | 01/01/70 00:00 | |
| 32 | 01/01/70 00:00 | |
| Jan. 20, 12:47:40 UTC | 01/01/70 00:00 | |
| Solution(?) | 01/01/70 00:00 | |
| Bible study | 01/01/70 00:00 | |
| EA must be connected ! | 01/01/70 00:00 | |
| up in the air | 01/01/70 00:00 | |
| Come off it, | 01/01/70 00:00 | |
| more than you believe | 01/01/70 00:00 | |
| I rest my case | 01/01/70 00:00 | |
well, the spec for the '32 stated it had | 01/01/70 00:00 | |
| it was not | 01/01/70 00:00 | |
| nope | 01/01/70 00:00 | |
| nope, he posted "Sorry, slipped in. Corr | 01/01/70 00:00 | |
| Corrected | 01/01/70 00:00 | |
| that is just absolutotally confoosing | 01/01/70 00:00 | |
| Just out of curiosity | 01/01/70 00:00 | |
| If I catch myself and it is e.g. an ambi | 01/01/70 00:00 | |
| ok so let's put it this way: | 01/01/70 00:00 | |
| OK | 01/01/70 00:00 | |
| sorry | 01/01/70 00:00 |