Thank you for using the ADTRAN Support Forums community.
First off, you definitely can use the T1 module and its interfaces for a Frame Relay connection.
As for timing, if the routers are providing timing, then the ATLAS should take timing from one router or the other (Slot 1.1 or Slot 1.2).
Your assumption is correct: you are mapping the Frame Relay endpoint to a physical interface, so the router connecting to that physical interface should have the same DLCI as you have configured on the mapped FR endpoint.
In your screen shot, I see you only have DS0 #24 mapped and not all 24 channels. I assume you want all 24 channels. To do this you must type in "1-24" otherwise you are only selecting the specific DS0 (like #24). This is probably why the Layer 2 is not coming up.
The "1:ERR" indicates that at least one port that is configured (mapped) on slot 1 is taking errors.
Hope this helps,
You sir are awesome! Selecting the DSO's range was exactly the issue. Also figured out the "1:ERR" was a clocking problem. Once the circuits came up the error went away but still showed clock slips - figured out that only one router needs to provide clocking and the other(s) can get clock from the other T1's across the Adtran. Very nice Would be better if the Adtran could get clock from NTP, but oh well.