NEO-257
| |
| 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.
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)