Atari had their own codes for BBSes and etc. I wrote a C64 Terminal that used ATASCII to allow a C64 to do the ATASCII cursor codes and etc. You needed a special font to see the Atari block characters the way they did. It was a modification of the BASIC Terminal that came with the VicMODEM.
Of course the Atari users didn't like the fact that I could view and log into their BBSes using ATASCII on a C64, so I eventually dropped it.