NEO-257

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Package QFP64R
Manufacturer
First use 1990 ?
Used on MV2B...

Quadruple 74HC257 2-to-1 multiplexer with common select line, making 16 switches in one chip. Used in dual slot MVS systems to select one of the two C ROM (and S ROM ?) buses.

Select signal comes from one of the "SLOT" outputs of NEO-F0 ?

MV2B @ L4 pinout

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

OpenOffice Draw file: File:Neo-257 L4.odg

MV2B @ K4 pinout

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

OpenOffice Draw file: File:Neo-257 K4.odg

MV2B @ J11 pinout

Used to switch between the onboard SM1 ROM / game M1 ROM, and onboard SFIX ROM / game S ROM.

OpenOffice Draw file: File:Neo-257 J11.odg

Pinout

Information provided by Channelmaniac.

File:Neo-257 pinout.png

OpenOffice Draw file: File:Neo-257.odg

  • A*,B*: Inputs
  • Y*: Outputs
  • Select: Output A if LOW, B if HIGH.
  • Some pins marked as ground could be "enable" pins
    • 35 is active high enable for entire chip
    • 18 is active low enable for Y0~Y7 (comes from "SYSTEMB" on a MV-2F and used to control /OE for FIXD0~FIXD7 from cart)
    • 33 is active low enable for Y8~Y15 (comes from "SDROM" from NEO-D0 to output cart M1 data to Z80)