I found this from searching for text "3a 3b 3c 3d 3e 3f 40".

https://archive.org/stream/bitsavers_ibm3720372nicationControllersExtendedServicesJul88_14791168/GA33-0066-2_3720_Communication_Controllers_Extended_Services_Jul88_djvu.txt
has a list of hexadecimal numbers from 0x00 to 0x7F after
"TRANSMIT CONTROL BYTE OR EOM SEARCH ARGUMENT
PADDING AND/OR SYNCHRONISATION CHARACTERS
TRANSMIT AND EXPECTED CHARACTERS:"
with this error:
"6A SB 6C"
maybe should be
"6A 6B 6C"