Dear Forum Members,

I have been using P89V51RD2 for my welding controllers. Several units aer working without any problem. My controllers use PCF8591 I2C ADC for some analog measurements. Since the ADC is I2C using P89V51RD2 I could get fewer samples since P89V51RD2 doesn't have a hard I2C engine in it and my soft routines wasted a lot of time doing I2C thus I couldnt fetch maximum samples.

In order to resolve this problem I switched over to P89C668 and today I had a trial with this micro rest all hardware and my Keil C program were kept the same. In Keil I changed the target chip and also changed the include file to #include<reg668.h>. The code compiled properly but when loaded to the device problem starts. The program does everthing properly except for one thing i.e. On LCD it display 'bbbbbbbbbbbbbbbbb' nothing else. The messages to be displayed on LCD are unsigned char strings in code space. I think something is wrong with fetching these strings from code memory. Initially I though may be something wrong with security bits and I cleared all security bits cleared all flash and reprogrammed but things didn't change I tried with 3 P89C668 virgin IC's but still the same results.

This is the first time I am using P89C668 with P89V51RD2 I never had this problem.

If required I will post the LCD code for inspection. But I would like to mention again that things work absolutely fine with P89V51RD2.

Thanks to all of you for reading my post.

Regards,
Prahlad Purohit