AM3270 and TR3271 Configuration and Management Manual

Overview of AM3270 and TR3271
AM3270 and TR3271 Configuration and Management Manual—529993-001
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AM3270:Pass-Through Configuration
AM3270 treats a successful SCF CONNECT as a combination of OPEN and READ.
File-system requests such as OPEN, READ, and WRITE are not accepted, because all
communication between an AM3270 subdevice and a TR3271 subdevice goes through
the message system.
The following section discusses these programs and interfaces in more detail. For
information about specific SCF commands, refer to later sections of this manual.
Data Transfer in Pass-Through Mode
When data is received from the host for a TR3271 pass-through subdevice, the data is
sent to the corresponding AM3270 subdevice. AM3270 then:
•
Selects the device
•
Writes the data
•
Completes the request to TR3271
•
Posts a READ to the AM3270 subdevice
AM3270 treats its end of the subdevice pair in a similar manner. The main difference is
that a WRITE request from TR3271 cancels the implicit READ at the AM3270 end
because AM3270 allows only one request queue per subdevice.
PTP between AM3270 and TR3271 passes all data from the IBM host, connected by a
multipoint line to a TR3271 tributary subdevice, to an AM3270 subdevice which passes
all data to the corresponding tributary device such as a terminal or printer. The
connection between AM3270 and TR3271 occurs over Expand.
Formatting in Pass-Through Mode
Neither AM3270 nor TR3271 perform buffer formatting or deformatting. Text passes on
a whole-message basis. In effect, AM3270 gathers all parts of a multiblock message
before sending it to TR3271. Similarly TR3271 gathers all blocks in a multiblock
message before sending data to AM3270.
Loss of Communication in Pass-Through Mode
In separate systems on a network, communication between line handlers is lost and no
special action is required.
PTP between AM3270 and TR3271 uses the Join/Break procedures as a form of
connection establishment and release procedures between the AM and TR subdevices
connected. Join/Break procedures ensure that the Expand connection between the AM
and TR subdevice pair is restored when either the AM or TR line handlers are
restarted.