Showing posts from March, 2005

Proposed Ethernet Board Layout

Here is sample of how the board will be layed out:

Design notes

Use a frequency of 4Mhz for the SPI bus. This will allow the Mega8 Atmel AVR chip to communicate over the same SPI bus as the MMC/SD cards will. Have a way to disconnect the SPI pins from the programmable logic chip so that in system programming of the Mega8 part can occur. Use a two byte 'window' for the ISA bus port. This will allow for 6809 assembly instructions such as LDD and STD to work where two bytes can be read/written faster. Have two bytes to determine the ISA address we are going to address. This will allow access to locations on the ISA bus from $0-$FFFF. Could add extra pins for greater address space if necessary.

WinCupl download and install

Installed and configured latest version of WinCupl from Atmel web site (version 5.30.4). For this project I am going to use the same CPLD part (Atmel ATF1508AS 84 pin PLCC 20ns part). According to the WinCupl fitter tool there are 50 percent of the I/O pins still available and only 20 percent of the internal logic is being used. This should allow for the ISA bus logic to be included in the same part. Here is my latest CPLD code for this project. The link is here . This code does not yet have any ISA bus logic added at this point :)


Worked further on CPLD pinout for ISA bus to COCO bus.

Start of Ethernet Project

Started an online record of my work to bring ethernet to the Color Computer 3 using OS-9 and my custom hardware.