HP Data Entry and Forms Management System (VPLUS) Reference Manual (32209-90024)

668 AppendixL
A Programmer’s Guide to VPLUS
VPLUS & Multiplexers
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.