HP 82718A Expansion Pod Reference Manual page 26

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Software Usage and Examples
Here is the simplest terminal program that does all three operations:
1 [1 t'1O D E t' 1 ot·4
2[1 MODOUT KEY$
~
DISP MODIN$;
~
GOTO
20
(Assumptions that allow this to work are: the modem is in its default state with command echoing enabled
(E 0)
and data echoing disabled
(G 0),
~HDTH
is
H4F
to avoid spurious
GR
.bis,
and
DELA'y'
is zero to
avoid long delays after each
D I
::;p is executed.)
................... .
Line 10 turns on the modem. If the modem is on, line 10 has no effect.
t'10DOUT KE\'$
gets the ASCII
character for any key pressed and sends the character to the modem. The character is put in the modem
transmit buffer. If the character is the command character, the subsequent characters typed will be
treated as part of a low-level modem command, until the command is terminated by a carriage return.
D I SF'
t'1OD
I
t·4$
displays anything in the modem receive buffer. The semicolon (;) inhibits the
~R l.iF
after the
D I ::;p
statement; without it, each block of characters read by
t'10D I t·U
would appear on a
separate line.
GOTO
20
repeats this sequence forever.
There are three things that can appear
In
the receive buffer: 1) modem responses,
2)
echoed low-level
commands, and
3)
incoming or echoed data. Responses always appear in the receive buffer. They can
only be shortened using the L (LONG) command-they cannot be suppressed entirely. Low-level
commands can be echoed either by the modem or by the terminal program. The host cannot echo the
commands because they are processed locally by the modem and not transmitted to the host. If command
echoing has been enabled (E 0), the modem will do the echoing. If command echoing has been disabled (E
1), the terminal program must do the echoing by using
D I
SP K$
to display everything typed:
1
[1
t'10D E t' 1 ot·4 I~
t'10DOUT
II
~':E 1
II
:~.:
CHF.:$'::
1::: ::.
2[1 K$=KEY$ @ MODOUT K$ ~ DISP K$;MODIN$; @ GOTO
20
Data can be echoed by either the host computer, the modem, or the program. If data echoing has been
disabled (G 0), the host is expected to echo the data. If data echoing has been enabled (0 1), the modem
will echo the data, regardless of the action of the host. If neither the host nor the modem is echoing the
data, the program must do so
(D I
::;p
K$).
These different approaches to command and data echoing are summarized as:
Host Modem Program Modem Terminal
echoes echoes echoes parameters program
data commands nothing
0
O,E
0
DISP MODIN$;
nothing commands nothing
G 1 , E
0
DISP MODIN$;
and data
nothing nothing commands
G O,E 1 DISP K$;MODIN$;
and data
25