AM3270/TR3271 Reference Manual

AM3270 Product Environment
A Closer Look at AM3270
3–6 086705 Tandem Computers Incorporated
AM3270 Product
Environment
Table 3-2 lists some of the features of AM3270 as they apply to Tandem NonStop
systems and to Tandem NonStop systems with a 3650/6100 CSS or a 3605/6105
controller. The 6202 controller is supported for C-series releases only.
Table 3-2. AM3270 Product Environment
Function 3650/6100 CSS
Maximum Devices/Line—253* YES
ASCII/EBCDIC Character Code YES
User-defined Translation YES
Maximum Line Speed—19.2Kbps YES
Screen Scroll in ITI Mode YES
General/Specific Polling YES
Printer Support YES
Terminal Screen Sizes—12x40, 24x80, 32x80, 43x80, 12x80 YES
Transparency NO
Elect. Interfaces—RS232/V24 YES
On-line Remote Diagnostics YES
Pass-Through to TR3271 YES
Control Utility SCF
* The figure quoted for maximum number of devices per line is an addressing limitation. The actual
number of devices configured for a line depends on the response time desired, as determined by
factors such as line speed, block size, and transaction rate.
Using Multiple-Level
Access Methods
AM3270 is a layered access method. Actions required to perform specific functions for
the file-system interface, the bisynchronous protocol, or the hardware driver are
handled within various levels of the access method. The I/O process accepts requests
from the file system and routes the requests to the appropriate level for processing.
AM3270 provides the following:
Level 1—the bisynchronous driver—interfaces with the line interface unit (LIU) in
the 3650/6100 CSS environment to set up and execute operations that result in the
transmission or reception of messages on the communication line.
Level 2—the multipoint supervisor—implements the Binary Synchronous
Communication protocol. Level 2 protocol is driven by requests from the request
processor (level 3 protocol) and by completed events from the driver (level 1
protocol).
Level 3—the request processor—accepts events from the I/O interface that may be
either file requests (for example, OPEN or READ) or externally generated actions
(for example, timeouts or SCF operations). Level 3 protocol preprocesses these
requests and determines whether the level 2 protocol is called or the appropriate