AM3270/TR3271 Reference Manual

Summary of Applicable File-System Procedures
A Closer Look at TR3271
5–10 086705 Tandem Computers Incorporated
For your information, the obsolete caveats are:
EOT delay
Handled within the 3650/6100 CSS, so no longer relevant to the CPU.
Conversational replies
Particularly in the area of buffer allocation, this applies only to TR3271 in a non-
3650/6100 environment. Although conversational replies are also supported for
TR3271 in the 3650/6100 environment, the actual function is handled within the
CSS itself.
Summary of
Applicable File-System
Procedures
Table 5-1 lists procedures that can be used by an application process as requests to
TR3271. However, note that with the exception of DEVICEINFO, pass-through
protocol (PTP) does not accept any file-system requests from application processes.
Table 5-1. Applicable File-System Procedures for TR3271
Procedure Action Performed
AWAITIO used to wait for completion of outstanding I/O operations.
CANCEL used to cancel any outstanding request.
CLOSE terminates access to a subdevice.
CONTROL initiates two-step READs.
DEVICEINFO returns the type and configured record length for the requested subdevice or line.
FILEINFO returns error information and characteristics of an open subdevice.
OPEN establishes communication with a subdevice. A subdevice may be OPENed up to
seven times at any given moment.
READ authorizes TR3271 to accept selects and text from the host on behalf of the
application. TR3271 performs the appropriate acknowledgment sequence without
intervention from the application.
SETMODE enables 3270 COPY operations and manipulation of status bits, and also provides
the ability to obtain the actual count of characters read by a two-step READ.
WRITE authorizes TR3271 to transmit text to the host in response to a poll.
Read and Write Operations TR3271 functions as one or more 3270 control units on a multipoint line. The host
(supervisor station) has control of the line and initiates all line operations.
A READ request from an application causes TR3271 to mark the subdevice as
“reading.” When the host performs a select operation to a subdevice which is reading,
the select is acknowledged, causing the host to send the data. When the host has sent
the data or a nonrecoverable error occurs, TR3271 completes the READ request to the
application.
A WRITE request from an application causes TR3271 to mark that subdevice as
“writing.” When the host issues either a specific poll to a writing subdevice or a
general poll to a control unit that has a subdevice that is writing, TR3271 responds to