NEO-E0

NEO-E0 chip found on a AES board.

Also found on MVS boards, even those without memory card slots.

BIOS vector table swapping

When 68k A8~A23 = 0 and the BIOS's vector table is chosen (by using the "system" memory mapped registers), A22I~A23I outputs are set to 1. This makes the address appear to address decoding chips as a BIOS access instead of a P ROM access.

Memory card address latch

On AES systems, BNK0~BNK2 are tied low. This makes the chip act just like a buffer ? What are BNK0~BNK2 used for ?

The chip also ANDs the pair of 8bit output enable signals from the NEO-C1 since there is only a single 16bit ROM used for the BIOS.

Pinout

• A1~A23: 68k address bus
• Y0~Y23: memory card address bus
• BNK0~BNK2: comes from NEO-D0, ?
• VEC: BIOS vector table swapping enable
• ANI0, ANI1, AND0: AND gate used to generate ROMOE from ROMOEU and ROMOEL