I am planning to use the P89C51RA2BN(40 PIN DIP), yesterday when I fired up the prototype I noticed a few things that did not quite agree with the data sheets.

1) The Reset pulse duration due to the Watchdog timeout was exactly 98 * Tosc, but I am using the 12 clock mode according to data sheet(p43), if I interpreted correctly, it should be 196 * Tosc.
2) Writing to the CKCON register did not make any difference, it is as though it is not there. The only way I can change the clocks is by using the parallel programmer.
Additionally, once the clock is changed to 6 using flash magic I am not able to bring it back to 12 clock unless I use a parallel programmer.

It is behaving like a H even though it has BN marked on it. Has anybody else seen this.

On an unrelated note, the WDT times out at about 16.4 msec (using 12 MHz Clock) this is too fast for me and creates unnecessary house keeping load on the micro, I am wondering if I should switch to Atmel to use their more flexible watch dog timer.

Please advice.

Thanks,
Nathan Iyer