HP 3000 Manuals HP 3000 Manuals
DTS Enhancements
By Stephen Lin/Regis De Poortere--Business Networks Division/Grenoble
Networks Division
The Distributed Terminal Subsystem (DTS) is released as part of the MPE
XL Fundamental Operating System (FOS), and provides asynchronous device
connectivity for terminals and serial printers. The DTS consists of the
Distributed Terminal Controller (DTC) hardware, the DTS host software,
and the DTC software downloaded to the DTC from the XL host. With the
exception of the system console, which has its own access port, all
terminals and serial printers are connected to the system through the
DTS. A single device I/O physical connection runs from the asynchronous
device to the DTC, and continues through the LAN cable to an XL host
system.
Two major enhancements are included in MPE XL Release 1.2. These
enhancements are Printer Type 26 for network printers and typeahead for
accepting data before a read is actually posted.
PRODUCT ENHANCEMENTS
The enhancements implemented by MPE XL Release 1.2 are detailed in the
following paragraphs:
Printer Type 26
The MPE XL Printer Type 26 is equivalent to MPE`V/E TT26. It allows
serial printers to be connected through two back-to-back HP 2334A
Statistical Multiplexers across a leased line or X.25 network to DTC
ports. Currently, HP 2334A Plus and HP 2334A Multimux with firmware
version Pass 3.2 or later are supported with Printer Type 26.
Printer Type 26 is a superset of Printer Type 22 with enhanced features
in the areas of status request generation, XON/XOFF flow control, and
modem signal manipulation.
In MPE XL, Printer Types 26 and 22 cause status requests to be generated
only at FOPEN, FCLOSE, and DCLOSE. For Printer Type 22, if the status
reply is not received within 60 seconds, a spoolee I/O error will appear
on the console and the spooler will stop. However, for Printer Type 26
an "ldev not ready" message will be shown on the console and the
60-second timer will be reactivated. The process can be repeated up to
10 times. If no status reply is received after 11 minutes, a spoolee I/O
error will be issued and the spooler will stop.
If the status reply received indicates a printer offline or printer
paper-out condition, a second status request will be sent to the printer.
This mechanism is implemented to resolve a possible deadlock situation
caused by flow control done locally at HP 2334A multiplexers. If the
status reply received indicates that the printer buffer is full, it will
be treated as a good status reply and the MPE XL will continue to send
data to the printer. This is possible because the DTC is responsible for
flow control.
The DTC keeps track of the length of time since an XOFF was received from
the printer. If an XON is not received within 60 seconds, an "ldev not
ready" message will be shown on the console. The timer will be
reactivated. The process may be repeated up to 10 times. If XON is not
received after 11 minutes, a spoolee I/O error will be generated and the
spooler will stop.
The modem signal behavior for Printer Types 22 and 26 is different. For
Printer Type 22, the Data Terminal Ready (DTR) modem signal will be
dropped for exactly 5 seconds after a file is printed. To prevent the
need for re-establishing the connection for every print file, Printer
Type 26 keeps the DTR signal high for 10 seconds after a file is printed.
If the next FOPEN is received within 10 seconds, no connection
establishment is needed, so data can be sent to the printer immediately.
In this way the remote printer on a modem port is able to print a string
of continuous print files without having to re-establish the connection
after every file is printed. If an FOPEN is not received within the
10-second time frame, the DTR will then be dropped. After the DTR signal
is dropped, it will be kept low for at least 10 seconds to allow the
network time to clear the connection. Only when the next FOPEN arrives
will the DTR be raised again to resume normal operation.
Typeahead
The typeahead facility is a new feature not implemented in MPE`V/E. It
enables a terminal user to input data before a read is actually posted.
The data entered before a read is posted is kept in a typeahead buffer in
the DTC. In this way the user does not need to wait for the system to
reply before typing other commands.
The typeahead mode is disabled by default. Typeahead can be enabled or
disabled on a per-port basis.
To enable typeahead, enter the following command:
:TYPE.DTS0000.TELESUP ON
To disable typeahead, enter the following command:
:TYPE.DTS0000.TELESUP OFF
In a future release, the typeahead mode will be enabled and disabled
through use of a CI variable.
When the typeahead mode is active, typing a backspace character will
erase the previously typed character but will not affect any commands in
the typeahead buffer terminated by carriage returns. Entering a
subsystem break or hitting the break key will cause all the data in the
typeahead buffer to be discarded. This provides the user with the
ability to erase previously typed commands.
The FDEVICECONTROL(192) intrinsic is used to programmatically set and
control typeahead mode. A control directive of 51 turns typeahead on or
off for a DTC port. A control directive of 60 allows the user to discard
any data in the typeahead buffer and receive characters directly from the
terminal for the next read. A control directive of 61 allows the user to
keep the typeahead data, and yet, receive the data directly from the
terminal for the next read only. For more information on programming for
typeahead refer to the MPE XL Asynchronous Serial Communications
Programmer's Reference Manual (P/N 32022-61001).
NOTE The typeahead facility should not be used with applications which
do not specifically code with the above-mentioned intrinsic for
typeahead processing.
Users may encounter problems if they try to run a VPLUS or user block
mode program while typeahead is enabled. In sequence, the application
program first sends an escape sequence to acquire the Terminal ID. Then,
if there is any data in the typeahead buffer, the data will be returned
to the application, which causes the application program to fail.
While the typeahead mode is active, the user should not attempt to change
the speed and parity setting.
PRODUCT CONFIGURATION
After MPE XL Release 1.2 is installed, the DTS must be configured through
NMMGR. The configuration procedure that should be followed will vary
according to whether the customer is installing the MPE XL system for the
first time or is migrating to Release 1.2 from a previously installed
Release 1.1 version. The procedures for each case are detailed in the
following paragraphs. For the overall installation and configuration
procedures, the user should consult the HP 3000 MPE XL Installation and
Update Manual (P/N 63123-90001).
Customers Installing MPE XL for the First Time
Customers who are using a Release 1.2 tape to install MPE XL on a
particular system for the first time should follow the procedure detailed
below:
1. Use FCOPY to create NMCONFIG.PUB.SYS using NMSAMP1 as the source
file, as follows:
:FILE nmconfig.pub.sys;dev=1
:FCOPY FROM=nmsamp1.pub.sys;TO=*nmconfig.pub.sys;NEW
2. Run NMMGR against the newly created configuration file to enter
the physical path for DTSLINK, and modify any parameters according
to customer's needs.
3. Validate the DTS subsystem and correct any problems before leaving
NMMGR.
4. Run SYSGEN to cross validate the system and data communication
configuration.
5. Reboot the XL system and power cycle the DTC(s).
In the NMMGR sample file, NMSAMP1, the physical path for the DTSLINK is
left blank. The standard physical paths for the DTS (as well as the NS
product) are differentiated according to the MPE XL host model and system
configuration. The physical path configured must always match the
physical slot in the host chassis that contains the LANIC card for the
DTS. Refer to "Appendix C" of the MPE XL Asynchronous Serial
Communications System Administrator's Reference Manual (P/N 32022-61000)
for information on which physical path should be specified for each
particular CPU that MPE XL is being configured.
NOTE The NMMGR validation will fail if the physical path for DTSLINK is
not provided.
If an incorrect physical path is entered, the NMMGR validation may
pass. However, at system boot time, DCC error messages will be
shown on the console and none of the DTC devices will work.
Customers Migrating from Release 1.1
Customers who have previously installed and configured MPE XL Release 1.1
and are migrating to Release 1.2 should run the NMMGRVER conversion
utility against NMCONFIG.PUB.SYS. The following procedure should be
followed:
1. Back up the existing configuration file.
2. Run NMMGRVER against NMCONFIG.
3. Run NMMGR to modify the configuration if there is any change.
4. Validate the DTS subsystem before leaving NMMGR.
5. Run SYSGEN to cross validate the system and data communication
configuration.
6. Reboot the XL system and power cycle the DTC(s).