NEO-257: Difference between revisions
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Four "74HC257" quad 2-to-1 multiplexers with | 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. | Used in dual slot MVS systems to switch between carts. | ||
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Select signal comes from one of the "SLOT" outputs of {{Chipname|NEO-F0}} ? | Select signal comes from one of the "SLOT" outputs of {{Chipname|NEO-F0}} ? | ||
== MV2B @ L4 | =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. | Used to switch the upper 16 bits of the sprite graphics bus. | ||
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OpenOffice Draw file: [[File:neo-257_L4.odg]] | OpenOffice Draw file: [[File:neo-257_L4.odg]] | ||
== MV2B @ K4 | == MV2B @ K4== | ||
Used to switch the lower 16 bits of the sprite graphics bus. | Used to switch the lower 16 bits of the sprite graphics bus. | ||
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OpenOffice Draw file: [[File:neo-257_K4.odg]] | OpenOffice Draw file: [[File:neo-257_K4.odg]] | ||
== MV2B @ J11 | == MV2B @ J11== | ||
Used to switch between the onboard [[SM1]] ROM / game [[M1 ROM]], and onboard [[SFIX]] ROM / game [[S ROM]]. | Used to switch between the onboard [[SM1]] ROM / game [[M1 ROM]], and onboard [[SFIX]] ROM / game [[S ROM]]. | ||
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OpenOffice Draw file: [[File:neo-257_J11.odg]] | OpenOffice Draw file: [[File:neo-257_J11.odg]] | ||
[[Category:Chips]] | [[Category:Chips]] | ||
Revision as of 22:23, 29 September 2016
| |
| Package | QFP64R |
| Manufacturer | 
|
| First use | 1990 ? |
| Used on | MV2B... |
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 NEO-F0 ?
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: File:Neo-257 L4.odg
MV2B @ K4
Used to switch the lower 16 bits of the sprite graphics bus.
OpenOffice Draw file: File:Neo-257 K4.odg
MV2B @ J11
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