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THE ETHERNET DEVELOPMENT BOARD

Part 1: Putting it all Together
by Fred Eady

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

ASSEMBLE THE PIC16F877 ELECTRONICS

If youýre familiar with PIC microcontrollers, there wonýt be any surprises on this side of the Ethernet Development Board. The PIC mounts in a 44-pin PLCC socket and is clocked at 20 MHz by the ceramic resonator XTAL2. Two gates of a 74LS125 buffer the program clock and program data lines from the PC parallel port. The program data gate of the 74LS125 is tri-stated during program data reads by one of the other parallel port pins in the PC.

Photo 8ýThereýs no solder paste shown in the photo, but use some here anyway.

To enter ICSP and LVP modes, you must be able to toggle the PIC16F877ýs RB3 and MCLR pins. The RB3 pin is directly controlled without buffering from a pin on the PCýs parallel port. A standard switching transistor uses a bit from the parallel port to toggle the MCLR line. Finally, pins 11 and 17 are shorted together to allow the PC application program to sense the presence of the Ethernet Development Board.

In addition to the PIC16F877 and its supporting components, youýll also find the CS8900A-CQ power supply bypass caps as well as magnetic support capacitors C8 and C9. Use Photos 8 and 9 to install the CS8900A-CQ bypass capacitors and magnetic support capacitors first.

Photo 9ýThis shot gives you a sneak preview of the rest of the PIC side of the Ethernet Development Board.

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