AM3270/TR3271 Reference Manual

Details of the PTP Protocol
TR3271 Subdevice Protocols
6–10 086705 Tandem Computers Incorporated
The SCF CONNECT command is used to join X1 to T2.
Subdevice T3 is configured in ITI mode because a command interpreter will be
started on this terminal.
The command interpreter IN and OUT files are $AM.T3.
Subdevice P1 is a printer configured in PTP mode and is controlled by AP3.
What About File System
Requests?
To TR3271, a successful CONNECT acts as a combination of an OPEN (EXCLUSIVE)
and a READ. File-system requests such as READ and WRITE are not accepted by
TR3271 for pass-through subdevices because there is no opener to perform such
requests.
Data received from the host for a TR3271 pass-through subdevice is sent to the
corresponding AM3270 subdevice. AM3270 selects the device, writes the data and
completes the request to TR3271. TR3271 then posts another READ on behalf of the
AM3270 subdevice.
In pass-through mode, no formatting or deformatting of the buffer is performed by
either AM3270 or TR3271. All text is passed on a whole-message basis; AM3270
gathers all blocks of a multiblock message before sending it to TR3271. TR3271 also
does this before sending a multiblock message to AM3270.
Communication Loss If communication is lost between line handlers in separate systems on a network, no
special action is taken. If the failure was due strictly to communication loss, the two
line handlers resume activity when communication is restored. If the failure was due
to a system failure/reload, a CONNECT can be performed again using the reloaded
system as the local system.
The remote end will accept these requests from a line handler/subdevice to which it is
already connected if no parameter changes occur (with the exception of subdevice
name).