AM3270/TR3271 Reference Manual

AM3270 Product Environment

A Closer Look at AM3270

086705 Tandem Computers Incorporated 3–11

A fully-qualified subdevice name consists of the line name and the subdevice name

specified by the user when the subdevice was added. A subdevice name is in the form

of #name, where the # character has significance to the file system.

The following is an example of a fully-qualified name that would be defined for the

OPEN procedure (in the following, b is a blank):

INT .TNAME[0:11] := [ "$AMLINEb#TERM1bb ", [ 4 * "bb" ] ]

, TERMNO;

TNAME[0:3] = $AMLINEb

is the line name associated with the AM3270 process.

TNAME[4:7] = #TERM1bb

is the name of the subdevice added by the user through SCF.

TNAME[8:11] = bbbbbbbb

is a filler, and should be specified.

To open #TERM1, the application process might contain the following statements:

CALL OPEN( TNAME, TERMNO, ...);

IF <> THEN do error processing

If the OPEN request is successful, TERMNO is set to the file number assigned by the

file system. Any subsequent requests by the application use TERMNO when

referencing the subdevice.

The specific mode in which a subdevice operates is determined by the level 4 protocol

assigned to it by the user. Each level 4 protocol provides the specific operational

characteristics of the physical device.

Each of the level 4 protocols for AM3270 (CRT display mode, printer mode, interactive

terminal interface, and pass-through mode) is described in a subsequent section.

Error Handling Error conditions that occur at the various levels are evaluated within AM3270.

AM3270 determines if the error can be handled by that level, passed to another level,

or returned to the application process.

Since the application process views the subdevice from a “request point of view” (that

is, the application issues various file-system requests to AM3270, that result in some

form of access or operation), AM3270 performs certain operations that are hidden from

the application process and translates the results into a form that the application

process can handle.