NEO-257: Difference between revisions

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Quadruple 74HC257 2-to-1 multiplexer with common select line, making 16 switches in one chip.
Four "74HC257" quad 2-to-1 multiplexers with some common select lines and output enables. Makes 16 switches in one chip (32 inputs, 16 outputs).
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]] ?
Used in dual slot MVS systems to switch between carts.
 
Select signal comes from one of the "SLOT" outputs of {{Chipname|NEO-F0}} ?


== MV2B @ L4 pinout==
== MV2B @ L4 pinout==

Revision as of 09:58, 29 September 2016

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

Four "74HC257" quad 2-to-1 multiplexers with some common select lines and 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 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)