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AN S-7600A/PIC16F877 JOURNEY

Part 1: Laying Out the Tools
by Fred Eady

Start ı Tooling Up ı Hardware Development Tool ı Software Development Tools ı Selecting a Terminal Emulator ı The Boot Loader ı Add Virtual Paper ı Sources and PDF

SELECTING A TERMINAL EMULATOR

Thank you Microchip application engineers! While researching this project, I read about a terminal emulator called Tera Term Pro in one of Microchipıs application notes. As it turns out, Teranishi wrote this emulator with the help of some nuclear physicists at the University of Tokyo and some of their Russian cohorts. That was enough for me, I had to have it. The great thing about Tera Term Pro is that, in addition to being a good script-driven terminal emulator, itıs free! Iıll be using Tera Term Pro in VT100 mode to send code to the S-7600A/PIC16F877 Internet Engine boot loader.

Thatıs the lineup. Serialtest Async will provide the play-by-play, as well as help with debugging the serial stream. The EDTP Internet Development board and accompanying software will act as the hardware test bed. Tera Term Pro will provide a highly automated user interface to the boot loader, and PCW will support the entire effort from the firmware side.

Hereıs how it will all connect in the development phase. The development board hardware is connected via a parallel interface to the development board software running on a Win98-laden PC. That same Win98 PC will also house and execute Tera Term and Tera Term macros. Tera Term communicates with the development board hardware via a serial interface that is monitored using the facilities of Serialtest Async, which is running on its own dedicated, highly powered personal computer. PCW is executing on the same Win98 machine with Tera Term Pro and the development board host software. All of the code generated using PCW is channeled through the development board driver to the development board hardware via the PCıs parallel port.

The objective is to produce an Internet-capable device that will interface to a computer (embedded, laptop, or otherwise) using a standard terminal program (Tera Term Pro). The Internet-capable device will incorporate a flash memory-based microcontroller (PIC16F877) that can be programmed using standard high-voltage techniques or with a custom boot loader program.

The boot loader will use the facilities of the terminal emulator to transfer executable code from the host computer to the microcontroller on the Internet-capable device. The PIC16F877 microcontroller is capable of self-programming. That is, the PIC16F877 has the ability to accept data via the custom boot loader program in its ROM and program this code into other areas of ROM within itself without assistance from external components or processes.

After the code is loaded via the Tera Term Pro/boot loader serial conduit, the PIC16F877 will begin execution of the newly loaded firmware. This firmware will control and communicate with an S-7600A Internet engine. Then, the S-7600A Internet engine will interface to yet another RS-232 port. Devices connected to the S-7600A via this RS-232 connection will most likely be modems. These externally connected modem devices will then allow the Internet-capable device to execute the tasks downloaded to the PIC16F877 ROM.

Because of its ability to be programmed easily via local methods or remotely, the Internet-capable device I am calling the S-7600A/PIC16F877 Internet Engine can be configured to be a web server, web client, or e-mail generator. In that the PIC16F877 is a full-function microcontroller with programmable I/O pins, the S-7600A/PIC16F877 Internet Engine also can be programmed to interact with its environment and capture data for transmission over the Internet to other S-7600A/PIC16F877 Internet Engines or Internet-capable devices or appliances.

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