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You can grab a copy of the 8008 User Manual here: https://www.manualslib.com/manual/943056/Intel-8008.html https://www.manualslib.com/manual/943056/Intel-8008.
by pwg 6y ago
You can grab a copy of the 8008 User Manual here:
https://www.manualslib.com/manual/943056/Intel-8008.html https://www.manualslib.com/manual/943056/Intel-8008.html
The 'download' link works, after possibly answering a google image captcha.
On pdf page 2 the "features" says the I/O lines are TTL compatible.
On pdf page 15 begins the "electrical specifications" section, and it looks like they just pull the outputs down against Vdd with a MOS transistor (see "Output Buffer" diagram in figure 7).
- egsmi 6y agoThanks! The pin out on page 2 has no ground, so what are they pulling down to? That’s my question. I can imagine a couple of ways to do make the TTL levels so I’m curious which way it was actually done.
- pwg 6y agoAccording to the diagram of the output buffer on pdf page 15, they pull down against Vdd (the negative supply). What is left unstated is that the pulldown transistor has likely been designed with a Vt such that when "on", and pulling down against Vdd, the output goes quite close to zero volts.