Hai,

For price computing weighing scale (very low cost), i am considering using 89c52 uC wit hte following:

1. 19 digits (for weight, unit price & total)
2. kEYS - 64MAX (key matrix)
3. SPI INTERFACE FOR A ADC
4. RS232
5. AC BUZZER
6. IIC EEPROM

The important processing is 19 digits software multiplexing and key scanning. I am going to use ASSEMBLY. If i initialize timer0 for a 1 milli second interrupt and tmr0 isr takes arround say 200 usec max.
RS232 will be interrupt driven. The SPI interface will be in SW. I can include AC Buzzer pulses in tmr0 isr.

Can i achieve the specs ? Your experiences will be the beginning point for me.

Regards,

V.Nagarajan