# What is the output logic levels of this STM32?

I am struggling getting my head around the input and output logic levels, mostly the output levels of this STM32 (STM32F446xC/E).

This table shows the output logic levels as dependent on if it is a CMOS, TTL, or something else which I don't know what kind of port. But how do I know if it is a CMOS, TTL or anything other? I can't find that information, only that all GPIOs are TTL and CMOS compliant, which I assume has to do with input rather than output.

What will be the output voltage levels? How do I know if my port is CMOS or TTL and thereby know which row of the table to read?

• Page 117 "All I/Os are CMOS and TTL compliant (no software configuration required)". – G36 Apr 15 at 14:55
• NOT possible for outputs to be TTL-compatible when $V_{DD}$ supply voltage is below +2.7V. – glen_geek Apr 15 at 15:00
• @glen_geek But how do I know if my output voltage will be a min. VDD-0.4 V or 2.4 V, as it depends on whether a CMOS or TTL port? – Robin Hellmers Apr 15 at 15:03
• Robin, there's only 0.1V difference between these. TTL outputs source a bit of current whereas CMOS outputs source NO current - this may account for the slight difference in these two specs. – glen_geek Apr 15 at 15:12
• @glen_geek Even more clarification from my side, how do I know whether my port is CMOS or TTL? It must be possible to know which of those specs that rule, no matter if it only is a 0.1 V difference. – Robin Hellmers Apr 15 at 15:15