| ??? 01/15/07 12:05 Read: times |
#130819 - Pins Responding to: ???'s previous message |
I said:
The voltage specs are in the table on p26 - "27. DC Characteristics" Adrian Worley said:
Hmmm, that table also does not specifically mention the serial port, just the parallel ports... Yes, but the serial port shares its pins (RXD, TXD) with Port 3, doesn't it? See "4.6 Port 3" at the top of p5. So, unless otherwise noted, the voltage ratings will apply to the pins - irrespective of whether they're used as P3.0, P3.1, RXD, or TXD. I said:
The AT89C55WD does contain an actual hardware UART; but that doesn't necessarily mean that your system is using it! Adrian Worley said:
Looking at the circuit diagram, the TXD and RXD pins on the chip run out to a small socket on the board. They do not appear connected to anything else, and in operation, nothing is plugged into that socket.
I can see in the program that there is some code involving timer1 and SBUF, but it all seems to be commented out. I infer from all this that whatever used to be connected to the TXD and RXD is legacy. Maybe it was just for debug? So, it seems that your systems does not actually use a "real" (by which I mean "physical hardware") UART - but, as previously noted, that should be of no concern to the bluetooth thingy. Unfortunately, there is nobody left here that knows anything about this hardware, and the documentation that exists, is sparse, and vague. I had to do some research to find out what the software language was as I'd never seen it before, (turns out it is something called PL/M). Yes - been there, done that. As a self-confessed non-hardware guy, don't you think it might be better to hire someone in to do this on a subcontract basis? You said you're short of staff - so is it wise to waste your time doing this, rather than what you "should" be doing? Just a thought. |
| Topic | Author | Date |
| AT89C55WD UART voltages. | 01/01/70 00:00 | |
| Level translation | 01/01/70 00:00 | |
| Thanks for that. | 01/01/70 00:00 | |
| Real? | 01/01/70 00:00 | |
| Real | 01/01/70 00:00 | |
| Reak! | 01/01/70 00:00 | |
| Voltage. | 01/01/70 00:00 | |
| Pins | 01/01/70 00:00 | |
| Pins | 01/01/70 00:00 | |
| the peculiar port structure of '51 | 01/01/70 00:00 | |
| The Socket | 01/01/70 00:00 | |
| Socket | 01/01/70 00:00 | |
| HW issues | 01/01/70 00:00 | |
| I am on the road, but someone can verify | 01/01/70 00:00 | |
| SN74LVC4245A | 01/01/70 00:00 | |
| 5V->3V conversion and vice versa | 01/01/70 00:00 | |
| If this is CMOS | 01/01/70 00:00 | |
| No insistance. | 01/01/70 00:00 | |
a link would be nice | 01/01/70 00:00 | |
| PLCC44 | 01/01/70 00:00 | |
| why AT89C55WD? | 01/01/70 00:00 | |
| Read the thread! | 01/01/70 00:00 | |
| AT89LV55? | 01/01/70 00:00 | |
| What is the blue tooth module? | 01/01/70 00:00 | |
| Module | 01/01/70 00:00 | |
| modules | 01/01/70 00:00 | |
| Modules | 01/01/70 00:00 |