NEO-253

NEO-253 chip found on a SLOT4F board.

Quintuple 74HC253 4-to-1 multiplexers with common select lines, making 10 switches in one chip.

Only (?) used on second revision 4-slot MVS systems. Not to be confused with the more common NEO-273.

Pinout

OpenOffice Draw file: File:Neo-253.odg

Select signals come from NEO-F0 SLOTA and SLOTB.

Todo: 10 and 42 are GND

SLOT4F @ 5E

• Mux 10~3: SDD7~SDD0
• Mux 2: PWAIT1
• Mux 1: PWAIT0
• Outputs go to CN9