P89C51RD2, 1)but the watch dog timer was interfering, thats what I think, while trying to download code using FlashMagic or WINisp, 2)In the current design, I am trying to remove the DS1232 and use the MCP810 in its place the MCP810 is also much smaller (SOT23).
1) The Internal WD in the Rx2 mast be started after each reset (it can not be stopped), thus, if you use the internal WD, there is no WD when downloading.
2) why do you not just forget about external WDs when you have an internal for free.

Erik

PS use the REAL WD, not the old Intel PCA4 Kluge.