An Implementation of Neptune-X: Network Interface Card for X680x0
The logic consisted mainly of an address decoder and an ISA bus bridge, the former implemented using one GreekPAK (SLG46826V-DIP) and one 74ALS15, the latter using another GreenPak. Note that some output pins are set to 'open drain'.
- neptune-x-adrdec.gp6: address decorder, a9-a8 buffer, reset inverter
- neptune-x-bridge.gp6: ISA bus bridge, irq inverter
The other parts (74ALS245 x2, 74AHCT245 x2) are tri-state bus buffers for address and data, some of which could be omitted.
The following items are RTL8019AS settings:
- Pull-up JP pin to set jumper mode (Cut under R3 'silk' and pull-up it)
- Pull-up IRQS2 pin to set interrupt line (Wire pin 16 and 28 of U2 using 4.7k ohm register)
I forgot to mention, cut the NE2000 card into a bite-size piece.
- Adjust timing in 68030 mode of Xellent30s
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Original Design
Neptune-X Home Page -
Implementation Example
Applause's Neptune-X -
Idea to ommit bus buffers
Neptune-X Compatible Simple LAN Board Production