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THE ETHERNET DEVELOPMENT BOARD

Part 1: Putting it all Together
by Fred Eady

Start ı Overview ı Elmerıs Silicon Glue ı Time to Kill ı The CS8900A-CQ ı Software and Firmware ı ICSP and LVP ı Assemble the Ethernet Electronics ı No Floating Allowed ı Installing the Bypass Capacitors ı Pin Point ı Finishing Installation ı Assemble the PIC16F877 Electronics ı The Rest of the Project ı Winding Down ı Finishing Up ı Sources and PDF

ICSP AND LVP

In addition to reading and writing PIC16F874 and PIC16F877 PLCC parts, the program uses the PIC16F8xxıs device ID field (location 0x2006 in the configuration area) to automatically configure the programming variables for the target part it senses. Program clock, program data, program mode, and MCLR control are the only control lines required to effect ICSP in LVP mode for the PIC16F877 parts.

Notice there are no high-voltage (13-VDC) components or voltages in Figure 2 or the Ethernet Development Board. LVP mode, which is triggered by a TTL high level applied to the ı877ıs RB3 pin, uses the standard 5 VDC applied to the PICıs V_CC pin to generate the required programming voltage internally. Because all of the control pins are operating at TTL levels, the PCıs parallel port is a perfect control line source.

Figure 2ıThe PIC16F87X series of PICs will program in-circuit with a minimum of external support electronics.

The Ethernet firmware is generated using Microchipıs MPLAB. After the Ethernet Development Board PIC code is assembled, the resultant hex file is loaded into the Ethernet Development Boardıs PC application programıs buffer and transmitted serially via parallel port bit banging to the target ı877 device on the Ethernet Development Board. Although it sounds complicated, itıs really a simple process.

If you need to get more on ICSP and LVP, go to the Microchip web site and pull up the PIC16F877 Programming Specifications. I wrote the PC application code based on the guidelines presented in that specification.

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