hi, i am building a cdi unit ( **broken link removed** ) but i am facing a problem , i can't find PIC16f628 nowhere,all i can find is PIC16f628A-i/p , and in the parts list (**broken link removed** ) PIC16f84AP is presented as replacement ,so can you tell me if it will work with either one , and do i have to make any changes to the circuit or the code . and which one should i use.
The differences between the 628 and 628A are very minor and in almost all circumstances the 628A will work as a direct replacement.
Some of the configuration bits are renamed although their function is still the same.
There is a change to the way code protection works, this shouldn't make any difference to functionality.
When TMR1 is tun in oscillator mode, it is optimized for 32KHz crystals instead of 200KHz.
For your application none of the differences are important and as it will work with the much older and simpler 16F84 it should work with the newer 628A.
Code sise limit is 1K in 16F84 wheras its 2K in 16F628. If your code is more than 1K, it won't fit in 16F84. There is some memory allocation difference too, which may or may not bother.