serial port and timer

if (a = 0) { ... }

is an assignment, i.e. it doesn't matter what value a had before your test. You must use == to compare, i.e.

if (a == 0) { ... }

Or reverse the two parts of the if/else and drop the explicit comparison:

if (a) {
    S0TBUF = '1';
    a = 0;
} else {
    S0TBUF = '0';
    a = 1;
}

You can also remove the if statement totally:

S0TBUF = '0' + (a++ & 1);

This extracts the odd/even bit of a, and continuously increments a.

if (a = 0) { ... }

is an assignment, i.e. it doesn't matter what value a had before your test. You must use == to compare, i.e.

if (a == 0) { ... }

Or reverse the two parts of the if/else and drop the explicit comparison:

if (a) {
    S0TBUF = '1';
    a = 0;
} else {
    S0TBUF = '0';
    a = 1;
}

You can also remove the if statement totally:

S0TBUF = '0' + (a++ & 1);

This extracts the odd/even bit of a, and continuously increments a.

The problem is that I want to stamp "0" then after a second "1", after another second "0", after another second "1" .... ect.With the instruction:

S0TBUF = '0' + (a++ & 1);

does it increase the value progressively?

"does it increase the value progressively?"

Per's post clearly described what it does - read it again, carefully...

As I already mentioned: "This extracts the odd/even bit of a". This means you will alternate between adding 0 and 1 to your printout, i.e. the printout will be 0101010101010101010101...

By the way - why do you want such a printout? It isn't exactly meaningful. You already have a toggling pin. Why emit trace output whenever you toggle the pin? Doesn't your pin toggling work?

Another thing: Why do you declare a as int? You are programming an 8-bit processor and int is in this case a 16-bit data type. Using a data type larger than the native register size is not recommended unless you need the range. In this case, your code only makes use of the values 0 and 1. You could use a 1-byte variable, or you could even modify your code to use a 1-bit variable.

In effects I don't know so much well to use the microcontrollore and I wanted something that alternatively stamped me to video "0" and "1" every second.

Another thing: Why do you declare a as int? You are programming an 8-bit processor and int is in this case a 16-bit data type. Using a data type larger than the native register size is not recommended unless you need the range.

The C167 is a native 16-bit microcontroller.

PS. I added the toggle to P2.0 since the Phytec board has LEDs connected to P2.

"It isn't exactly meaningful."

No - it's a homework assignment!

I was completely convinced that I saw C51 as architecture when I wrote the comment.

Anyway, a number of embedded processors has limited RAM space and special instructions for bit variables, so all variables should get their type based on a consious decision.

Yes, I thought as much, just wanted to point this out for other users.

I would just make a comment to the generated code for the C166 is usually (from a code standpoint) not as efficient when using a byte variable over a word variable (usually you end up with an extra instruction).

Per as you stated the user must decide what memory allocation is important for their application. I also appreciate your suggestion of an add instruction instead of an if statement.