SparkFun Forums

[Professor Chaos]

I am looking at the spec sheet for the ID-12 reader. Pin 8 is described as "CMOS" and Pin 9 is described as "TTL Data (inverted)"

Just what do those mean?? I am assuming pin 9 is some sort of serial protocol (care to guess a baud rate), but what does CMOS mean? Also a serial signal but at 3.3 V??

[Philba]

Probably the difference between CMOS and TTL voltage levels. You use the CMOS output with cmos logic (74HCxx for example) and TTL with ttl logic (74HCT, 74LS and so on). Look at the following chart. Check the data sheet of the device you are hooking up to.