I/O Blocks, Common Interface Nets.

We will consider a number of I/O blocks. All will be targets, most will also generate interrupts and some will also be initiators.

We use no bi-directional (tri-state) busses within our SoC: instead we use dedicated busses and multiplexor trees.

We use the following RTL net names:

• addr Internal adddress selection within a target,
• hwen Asserted during a target write,
• hren Asserted during a target read,
• wdata Input data to a target when written,
• rdata Output data when target is read,
• interrupt Asserted by target when wanting attention.

On an initiator the net directions will be reversed.