Hi I have aprogram that runson p89c51 and p89v51 when I am usunf an exact baudrate divider. I had to change my crystal and I have 3% error. the p89c51 keeps working fine and the p89v51 works in an unexpected way. Does someone experienced such a problem?
Thanks The original project was developed on P89c51RD2 with 22 MHZ. when we moved to P89V51 it worked OK. now we changed the clock input to about 35MHZ. the p89c51 keep working as expected and the p98v51 works but in an unstable way. We compile the project for the "V" device. the difference between the original to the current exept for the crystal speed is that the baud rate has an error of 3% which was not in the original project. can this be the problem? does the "V" version is more sensetive?
can this be the problem?
That's quite impossible to say --- you haven't spent as much as a single word on describing what "the problem" actually is!
The problem is just what I wrote .the p89c51 works in both cases the same. the p89v51 works on the slow speed just like the p89c51 but on the higher speed , the communication sometimes works and sometime not... i can not figure why only part of the communication works... the problem is that the p89v51 does not behave like the p89c51 in the higher speed. it becomes unstable.
.
No, X2
the max crystal for X2 is 20MHz
I am using 17.734 its about 35.... after X2 configuration
try T2 clocking and get the 3% error removed. You are running on the edge of acceptable and at that point a capacitor tolerance can make the difference.
Erik
Thanks! with timer 2 it works. (0.49% error)
It means that we should not take for granted that the p89v51 is 1 to 1 substitute for the p89c51...
NO, It means that we should not take for granted that ANY 'identical' chip is 1 to 1 substitute for the p89c51 when running outside margins