Hi All H/W system has: 1) 89C51RD2 (MC) 2) DS1232 as system reset IC ( Resets sys,if its strobe pin in not toggled in 1.2 Sec). In normal execution mode 1 port pin of MC toggles strobe pin of DS1232 before 1.2 Sec expires. ISP feature of 89C51RD2 is to be used for loading hex file in its flash. Since strobe pin is not toggled in ISP mode,DS1232 keeps on resetting system. and hence ISP is not able to load hex file. Sorry to say that this problem is not related to keil. can anybody provide way out of this if any one who have faced this problem. rgds Naresh
Erik Mark is correct, there are other reasons above that also: 1)internal watch dog timer in RD2 is providing less time delay hence has to be refreshed frequently.system is performing process which takes on average 1 sec to execute and during this period i do not want watch dog to be refreshed/reset my system. 2)Board has additional chips(other than MC):some require --> /rst and others --> rst. so best was to use external watchdog/reset IC,which will make system reset efficient. -------------------------------------------- regarding reset IC & ISP,best is to use seperate RC reset ckt for MC while it is in ISP mode. Rgds Naresh