IBM Bus & Tag channel protocol specs?

Sridhar Ayengar wrote: are the for hooking an aix box as a device to the mainframe, or vice versa? I believe there was discussion on the Hercules group, and there was no support for running Bus/Tag devices from AIX. It is meant to allow an AIX box to do something like support operations as a communications controller or other to the Mainframe. I believe that even IBM has put in dual interfaces on devices to allow them to be accessed from multiple hosts, such as tape libraries haveing both Bus / Tag for the mainframe (or Escon) as well as being scsi targets to the AIX boxes, etc. Bus/Tag is only one way, there is no way to have a device pretend to be a Host in the hookup, as far as the protocols and handshakes are concerned. That is why channel to channel adapters take 4 sets of hoses to do a connection between two mainframe, for example. Two (Bus/Tag) each way. Jim