Select target for chip enable logic line

Thread Starter

fc_aac

Joined Aug 25, 2017
2
I'm modifying my SEGA Dreamcast with a piggyback bios following this straightforward schematic.
If possible, instead of hacking a hole in the side of the case to install the SPDT switch, I'd like to instead run a line to the already present lid detect switch which, as far as I can tell, is a DPDT but is functionally connected as a normally open SPST which when closed grounds out the net.
I'm thinking I can harness this behavior as the input for a demultiplexer to select rom vs flash chip enable depending on the state of the disc lid.

Searching for 1:2 demultiplexer yields NL7SZ19.
I'd appreciate any comments on whether this seems like an appropriate approach for what I am trying to achieve.
 

DickCappels

Joined Aug 21, 2008
6,185
Your first link, apparently to a schematic, is broken. Can you paste the schematic directly in to your post or upload it to you post?
 

Thread Starter

fc_aac

Joined Aug 25, 2017
2
I got antsy and went to the local shop and picked up a 74hc139. Maybe overkill but it was only a dollar and I can make progress immediately. I'm going to tie the unused inputs to ground.
 

Attachments

Top