While we are stuck in the fault tracing I decided to start working on an expansion backplane. We wanted a possibility to add expansion cards to the µLind system and we settled on following requirements for the backplane:

• 6 expansion cards.
• 2 of the ports should have a complete address bus to it (for use with DMA functions for example.
• 2 sockets for 512kB ram, for up to 1MB of expanded ram.
• Possibility to chain one more backplane to the first for additionally 6 ports and 1MB ram.
• Slot for I2C expansion, giving the backplane a way of auto configure the different added expansion cards.
• Possibility to add RTC clock.
• Own address handler and IRQ handler.

So below is a picture of the first draft of the Expansion Backplane: