Issue 101 December 1998
em Ware Top to Bottom
Part 2: Launching the Application

THE PURPOSE

The idea here is to open up the PIC16C73 to the programmer. The PIC16C73 is register based, including the I/O ports. So, you can send a command to read and write a particular register via an EMIT/web-browser interface. As you saw, this little application does nothing but set everybody up and wait for work. The real work is performed in the two functions shown in Listing 7 called Poke and Peek.

These functions are tied to EMIT using a configuration .ini file. Peek and Poke are defined as exports in the .ini file along with any variables tied to EMIT’s GUI widgets.

Since Peek and Poke are defined in the configuration file, EMIT can generate code and addresses for them in its internal tables. Data is transferred between the PIC functions and EMIT via two buffer areas within EMIT.

These buffer areas are addressed as payload and replydata, the receive and send buffers. EMIT places data into the payload buffer area and then makes a call to the desired function, which places any data to be returned in replydata .

EMIT picks up this data and applies it to a variable that is represented by a GUI widget in the web- browser window. Listing 8 is an excerpt from the config.ini file that shows how the variables and functions are defined to EMIT.