NEO-257

Four "74HC257" quad 2-to-1 multiplexers with a common select line and separate output enables.

Makes 16 switches in one chip (32 inputs, 16 outputs).

Used in dual slot MVS systems to switch between carts.

Select signal comes from one of the "SLOT" outputs of ?

=Internal logic=

This is NOT verified.

See https://github.com/neogeodev/SNKVerilog/tree/master/NEO-257

=Pinouts=

Information provided by Channelmaniac. Some pins marked as GND could be "enable" pins.


 * A*, B*: Inputs
 * Y*: Outputs
 * 17 SELECT: A if low, B if high
 * 18 is an active low output enable for Y0~Y7
 * 33 and 34 are probably ORed together to provide an active low output enable for Y8~Y15
 * 35 is an active high enable for entire chip

MV2B @ L4
Used to switch the upper 16 bits of the sprite graphics bus.



OpenOffice Draw file:

MV2B @ K4
Used to switch the lower 16 bits of the sprite graphics bus.



OpenOffice Draw file:

MV2B @ J11
SYSTEM and SYSTEMB might be reversed ?



OpenOffice Draw file: