VPLUS & Multiplexers

Using VPLUS on a Pad-Terminal(Connected to a Cluster Controller HP 2334A)

What is a CLUSTER CONTROLLER?

When you use a Packet Switching Network (PSN) for data communication, you need equipment to do the packing and unpacking of the data at both ends. A CLUSTER normally will receive the packets for different users, unpack them and change the transmission mode from synchronous to asynchronous. This way you can connect several different asynchronous devices, such as printers and terminals to one X.25 packet line (on a HP 2334A up to 16).

At the computer side you can use another CLUSTER and connect the asynchronous ports to the ATP or ADCC ports of the HP 3000. This kind of connection is called STATISTICAL MULTIPLEXER.

Figure L-1 Statistical Multiplexer

The other way is to connect the X.25 packet line directly to an INP-card in the HP 3000 computer. To support the INP, you need special DS- or NS-software. The software and the INP-card will do the packing and unpacking of the data received. This configuration is the CLUSTER CONNECTION and we call it Packet Assembler / Dissassembler (PAD).

Figure L-2 PAD or CLUSTER Connection to an HP 3000 with an INP

First we will describe the minor differences between using the terminal directly to an ADCC / ATP port on an HP 3000, or to a port on a PAD (HP 2334A).

Terminal configuration when used to a direct line (ADCC / ATP):

Figure L-3 Direct Connection to an ATP- or ADCC-Port

DATACOMM :  BaudRate : line speed (9600, 4800, 2400, 1200, ..) 
  Parity/Bits: Par/# of bits (None/8, 0'S/7, ODD/7, EVEN/7) 
  Enq/Ack : YES use enq/ack handshake 
  Asterisk : OFF no indicator is shown 
  Chk Parity : NO we don't check for parity errors 
  SR(CH) : LO we don't select any Baudrate 
  CS(CB)Xmit : NO we don't use modem signals 
  RecvPace : NONE no XON and XOFF handshake is done 
  XmitPace : NONE on receive or transmit




	NOTE: Do not turn RecvPace or XmitPace to on at a 2392A terminal if it is connected directly to an HP 3000. An XOFF (ctl S) could hang the terminal. (Only POWER-OFF the terminal will reset this situation).

TERMINAL :Datacomm/ExtDev : PORT1/PORT2 
Keyboard : USASCII (or other keyboards) 
LocalEcho : OFF the HP 3000 will echo 
CapsLock : OFF we allow upper and lowercase 
Start Col : 01 start column 
Bell : OFF no right margin cell 
XmitFnctn : NO move- and editor-keys are not transmitted to the computer SPOW : NO spaces will overwrite existing characters 
InhEolWrp : NO no wraparound at the end of line 
Line/Page : LINE transmit one line at a time 
InhHndShk : NO enable XON / XOFF handshake 
Inh DC2 : NO ignored 
Esc Xfer : NO transmit esc-sequences to the printer 
TermMode : HP use HP special sequences

When you want to connect the terminal to an HP 2334A CLUSTER (PAD) you must change the following specifications:

DATACOMM: RecvPace  : Xon/Xoff              use XON/XOFF handshake 
 XmitPace  : Xon/Xoff              on send and receive transmission.TERMINAL : InhHndShk : YES                   disables the use of DC1- 
 Inh DC2   : YES                   and of DC1/DC2/DC1- 
                                   handshake on blockmode.

With the reconfiguration of the terminal you switch off the handshake normally used. For example: you do not use an XON and XOFF protocol between the computer and the terminal to control the dataflow on a direct line. The terminal does not transmit XON or XOFF (DC1 and DC3) automatically, this only can be sent by pressing the 'CTRL Q' or 'CTRL S' key combination.

The CLUSTER must be configured to use the PROFILE 1 to work properly.

The HP 3000 must have a PAD-terminal configured in the system like this:

DRT#        = ldev of inp        UNIT      = 0           CHANNEL = 0 
TYPE        = 16                 SUBTYPE   = 0           REC.WTH = 40 
DRIVER NAME = IOPAD0             DEV.CLASS = PADTERM

If you want to use VPLUS on the terminal connected to an HP 3000 via a port on a PAD (HP 2334A), you need a terminal supporting blockmode. For example:

HP 2382A, HP 2392A-2394A, HP 700/92-700/94 or similar.

One of the problems will be the transmission of a block after pressing the ENTER key. Normally the HP 3000 will control the dataflow with the normal DC1 and DC3 handshake (XON / XOFF). When starting VPLUS, the Application reconfigures the terminal, so it will use a handshake named DC1/DC2/DC1. By using this protocol, the computerside tells the terminal, that the FORM is transmitted completely and that the user may start entering data to the FORM. This is initiated with the signal DC1.

When the input is terminated either with an ENTER, a SELECT or a function-key, the terminal tells the ready-state of the data to the computer with the DC2-signal. The computer now will initiate the transmission with the signal DC1.

VPLUS                     TERMINAL                USER -----------------------I------------I----------------------------- 
                       .            . 
send a FORM ---------->.            . 
                       .            . 
FORM is ready,         .            . 
data can be            .            . 
entered                .            . 
DC1------------------->.            . 
                       .            . 
                       .            .           The User can 
                       .            .<--------- start typing. 
                       .            .
                       .            .<------ ENTER or Function-key 
                       .            . 
                       .Data is ready 
                       .to be       . 
                       .transmitted . 
<----------------------.DC2         . 
                       .            . 
VPLUS is ready         .            . 
to receive the         .            . 
data                   .            . 
DC1------------------->.            . 
                       .            . 
                       .Terminal sends 
                       .the data    . 
                       .entered to  . 
<----------------------.the computer. 
                       .separated with 'us' 
                       .and terminated with 'rs' 
                       .            . 
after receiving        .            . 
the last block         .            . 
VPLUS starts the       .            . 
execution and          .            . 
continues with         .            . 
the next FORM--------->.            . 
                       .            . 
----------------------------------------------------------------

This handshake does not work when you use your terminal on a PAD. The PAD itself catches the DC1 and DC3 signals or generates them as needed. So you can not use them to specify the transmission between the computer and the terminal, or to use the DC1/DC2/DC1 handshake for blockmode applications.

The alternative is the use of the term=24 in the LOGON like this:

HELLO paduser,user/usrpass.account/acctpass;TERM=24

This terminal type does not exist as a Term-Type file. The only program that requires it as a parameter, is VPLUS (and all VPLUS using applications). VPLUS checks this parameter and if the terminal type is decoded to be 'type=24', then there will be a special handling of the FORMS.

Normally when starting the blockmode, the application will check the configuration of the terminal with the sequence 'esc^^' and 'esc~'. Additionally it will check if the terminal is able to SPOW. Thereafter it will switch the terminal with the escape sequence 'ecs&s0h1G' to do the DC1/DC2/DC1-handshake.When using TERM=24, the application first will set the InhHndShk=Y and the InhDC2=YES with the escape-sequence 'esc&s1h1G'. You should set this before you start the session, but if you forgot, VPLUS will do it for you (but other things could go wrong, so it's better to do it yourself to be sure!). This sequence will switch off all handshakes. After this, the terminal will be checked like usual. Additionally the terminal will be set to lock the keyboard every time the ENTER or one of the Function-Keys is hit. This is done with the sequence 'esc&k1K'. It will prevent the user from entering data before the new FORM is rebuilt completely, and the keyboard is unlocked with 'escb'. This is necessary because the normal handshake with DC1/DC2/DC1 does not work here.

 VPLUS Terminal User ------------------------I---------------I------------------------ 
. . 
the keyboard will be    .               . 
locked, before the      .               . 
transmission of a FORM  .               . 
'esc c' --------------->.               . 
                        .               . 
now the transmission    .               . 
of the FORM will start  .               . 
FORM ------------------>.               . 
                        .               . 
when the FORM is ready  .               . 
the keyboard will be    .               . 
unlocked with           .               . 
'esc b' --------------->.               . 
                        .               . now the user can 
                        .               . start to enter . .<---- data 
                        .               . 
                        .               .<- ENTER or function-key 
                        .               .   this automatically 
                        .               .   locks the keyboard . . 
                        .start transmitting 
                        .of the data    . 
<---------------------- .entered        . 
                        .separated with 'us' 
                        .and terminated with 'rs' 
                        .               . 
when the FORM is        .               . 
received completely,    .               . 
VPLUS goes on and       .               . 
continues with the      .               . 
next Form ------------->.               . 
                        .               . 
                        .               . 
and unlocks the keyboard.               . 
after the the FORM      .               . 
transmitted completely  .               . 
'esc c' --------------->.               . 
                        .               . 
-----------------------------------------------------------------

The difference between the use of VPLUS on a direct line and a PAD is just the kind of dataflow control. The problem comes up only by the intelligence of the CLUSTER CONTROLLER which tries to prevent his memory or that of the terminal from overflow. This problem is solved by using 'term=24' in the logon. If you want to use VPLUS applications on a specified PADTERM, you can configure the terminal type in the system configuration to be '24'. This will switch on the correct blockmode handling for every user on this logical device.

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Using VPLUS on a Pad-Terminal(Connected to a Cluster Controller HP 2334A)