SNA IMF intrinsics can be divided into two categories: intrinsics
used with standard (wait) MPE I/O, and intrinsics used with no-wait
MPE I/O. With standard MPE I/O, a program that has issued an I/O
request must suspend activity until the I/O request has finished.
With no-wait I/O, or unblocked I/O, a program that has issued an
I/O request may continue processing and issue additional I/O requests
without waiting for previous I/O requests to finish. No-wait I/O
overlaps the processing of multiple I/O requests, overlaps I/O with
CPU processing, and responds to the completion of the first of several
outstanding I/O requests.
Standard MPE Wait I/O |
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A program using standard MPE wait I/O must suspend activity
after issuing an I/O request until the request has finished. It
cannot issue another I/O request until the previous request has
finished. Table 2-1 “SNA IMF Intrinsics, Wait and No-Wait I/O” shows the intrinsics that
can be used with standard (wait) MPE I/O. These intrinsics can also
be used with no-wait MPE I/O.
Table 2-1 SNA IMF Intrinsics, Wait and No-Wait I/O
Intrinsic | Function |
|---|
| ACQUIRE3270 | Allows your program to start Pass Thru on your
own terminal or on any free terminal or printer that is not under
MPE control. |
| ATTRLIST | Returns the locations of attribute characters
within a specified subsection or within all subsections of a screen. |
| CLOSE3270 | Emulates turning off a specified device. |
| ERR3270 | Returns the error message associated with a
given SNA IMF intrinsic error number. |
| EXTFIELDATTR | (for Asian users) Returns information about
the attributes of a specified field, including the DBCS attribute. |
| FIELDATTR | Returns information about the attributes of
a specified field. |
| OPEN3270 | Emulates turning on the power of an emulated
IBM 3278 display station or 3287 printer. The OPEN3270 intrinsic allocates the internal screen image
used by SNA IMF. |
| PRINT3270 | Produces a hard copy of the internal screen
image. |
| READFIELD | Reads a field of data from the internal screen
image and returns the data to an HP application program. |
| READSCREEN | Reads all or a specified part of the internal
screen image and returns the data to an HP application program. |
| READSTREAM | Reads all or part of the untranslated host
data stream. |
| RECV3270 | Allows your program to receive the screen after
modification by the host. Also informs your program that the host
has just sent data. |
| RESET3270 | Emulates pressing the [RESET] key on an IBM 3278 display station keyboard. |
| SCREENATTR | Returns information about the attributes of
the internal screen image. |
| STREAM3270 | Emulates typing a series of keystrokes on an
IBM 3278 display station keyboard. Allows you to do special function
key operations and to update multiple data fields with one intrinsic
call. |
| TRAN3270 | Emulates pressing one of the transmit keys
on the 3278 display station keyboard. TRAN3270 sends modified data to the host the next time
the host polls the device. |
| VER3270 | Returns the number of the version of SNA IMF
that is being executed on the HP 3000. |
| WRITEFIELD | Writes data from the HP application program
into an unprotected field of the internal screen image. |
| WRITESTREAM | Creates the data stream that an HP application
program sends to the host. |
No-Wait MPE I/O |
|
No-wait MPE I/O requires MPE privileged mode (PM) capability. However,
you do not need PM capability to write an SNA IMF application that
uses no-wait I/O, because the SNA IMF intrinsics themselves have
PM capability. When your application calls the SNA IMF OPEN3270 intrinsic with bit 15 of the flags parameter set to 1 (the no-wait I/O option), your program
can call any of the SNA IMF intrinsics with no-wait I/O, whether
or not you have PM capability.
If you do not have PM capability, SNA IMF intrinsics are the
only intrinsics you can call with no-wait I/O. If you call, for
example, the MPE FREAD intrinsic, your program will suspend processing
until the I/O request has finished, even though you specified no-wait
I/O in your OPEN3270 intrinsic call.
If your program will use no-wait MPE I/O, it must be written
in COBOL II, FORTRAN, Pascal, C, or SPL. The IOWAIT and IODONTWAIT intrinsics, which are used with no-wait I/O, return
a functional value, pass parameters by value, allow a variable number
of parameters, and set condition codes. Neither COBOL nor BASIC
has these capabilities.
Table 2-2 “SNA IMF Intrinsics, No-Wait I/O Only” shows the intrinsics used only
with no-wait MPE I/O. Two of these intrinsics, IOWAIT and IODONTWAIT, are actually MPE intrinsics. You can call them
directly using SNA IMF/V, but if you are using SNA IMF/XL, you must
use the SNA IMF/XL intrinsics IOWAIT3270 and IODONTWAIT3270, which in turn call the MPE intrinsics
IOWAIT and IODONTWAIT.
In addition to the intrinsics listed in Table 2-2 “SNA IMF Intrinsics, No-Wait I/O Only”,
all of the intrinsics listed in Table 2-1 “SNA IMF Intrinsics, Wait and No-Wait I/O” can
be used with no-wait MPE I/O.
Table 2-2 SNA IMF Intrinsics, No-Wait I/O Only
Intrinsic | Function |
|---|
| ABORT3270 | Aborts an outstanding no-wait RECV3270 or TRAN3270 request. |
| IODONTWAIT | (SNA IMF/V only) Informs a user program that
a previous I/O operation has completed. |
| IODONTWAIT3270 | (SNA IMF/XL only) Informs a user program that
a previous I/O operation has completed. |
| IOWAIT | (SNA IMF/V only) Waits for a previous no-wait
I/O request to complete. |
| IOWAIT3270 | (SNA IMF/XL only) Waits for a previous no-wait
I/O request to complete. |
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 | WARNING! Privileged mode bypasses the normal checks and restrictions that
apply to standard users (those using blocked I/O). It is possible
for a privileged mode program to destroy file integrity, including
the MPE operating system. On request, Hewlett-Packard will investigate
and attempt to resolve problems resulting from using privileged
mode. Although this service is not available under the standard
service contract, it is available on a time and materials basis.
Hewlett-Packard does not support, under any type of contract, corrections
or changes to the MPE operating system. |
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