NEO-253

Quintuple 74HC253 4-to-1 multiplexers with common select lines, making ten 4-to-1 switches in one chip. Used to switch read-only buses. The inputs are named according to the related slot: A is slot #1, B is slot #2...

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

=Pinout=



OpenOffice Draw file:

Select signals come from SLOTA and SLOTB.

SLOT4F @ 5E
Cartridge wait cycle configuration and Z80 bus.


 * Mux 1: PWAIT0
 * Mux 2: PWAIT1
 * Mux 10~3: SDD7~SDD0

Outputs go to CN9.

SLOT4F @ 5D
Sprites and fix layer graphics.


 * Mux 1: CR30
 * Mux 2: CR31
 * Mux 10~3: FIXD7~FIXD0

SLOT4F @ 5C
Sprite graphics.


 * Mux 10~1: CR29~CR20

SLOT4F @ 5B
Sprite graphics.


 * Mux 10~1: CR19~CR10

SLOT4F @ 5A
Sprite graphics.


 * Mux 10~1: CR9~CR0