Hi Members,

Thanks to all of you for your contribution.

I have made a list of following solutions for contention and ISP entry problems.

1. Use an invertor between DE and micro port pin to prevent contention.

2. Use a separate pin for /RE without an invertor as Russell suggested.

3. If I use common control for DE and /RE without invertor there is risk of contention If I use invertor there is a risk of errorneous ISP entry P89V51RD2. [ I have sent an e-mail to Andrew for his suggestions of this possible problem ].

4. Split the data byte to be transmited into two nibbles and make a byte out of each nibble by appending the high nibble with 0s to get two bytes. This way the data will always be 0x00 to 0x0F and it will never be 'U'. This will prevent any errorneous ISP entry of P89V51RD2 at startup. Thanks to Mr. Kiran V. Sutar [8052.com member] for his this suggestion that he gave me during our telephone covnersation.

5. Use a derivative that doesn't autobaud ISP every time it turn on I am looking at possibility of using P89C668 / P89C664 for this application. I wish this chip wont become obselete in very near future. I am sad seeing P89C51RD2 getting obselete.

Thanks & Regards,
Prahlad Purohit