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then
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H
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ls 20
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Software Usage and Examples
The program for the originating modem is as follows:
10
!
This ModeM is set to ORIGINATE Mode
20 MODEM ON
!
Turn on ModeM
~:[1
t'10DOUT
II
~·~o
II
g.:CHF.::t
0::
1:::::'
!
Ent et- OR I G
H~ATE
r'10de
40 IF NOT HOOK? THEN 40
!
Wait until ModeM is off-hook
50 ON l+HOOK?+CARRIER? GOTO 60,50,70
6[1
DI::W
IIt·k,
connect ion
ll
I~
BEEF' 220,1
IE! ::::TCIF'
7t1
D I
::W
II
Connect i on est ab I i shed
II
80 MODOUT KEY:t
~
DISP MODIN:t;
~
GOTO 80
Line
30
is the only difference between the two programs-the first program enters
ANSWER
mode by
executing the
A (ANSWER)
command, and the second program enters
ORIGINATE
mode by executing the 0
(ORIGI NATE)
command. Line
50
controls the program flow while the two modems are establishing the
communica tion link. It is the same self -timing technique described in the section "Detecting Connection
With a Remote Computer". Line 40 is necessary so that the program will not halt immediately before the
A
and
0
commands have taken the modem off-hook. Line 80 allows one modem to transmit data typed in
from the keyboard and transmit it to the other modem, and to display data received from the other
modem.
Notice that lines 20 and 80 together constitute the simple terminal program described in "Terminal
Program" earlier in this section. You can use just this terminal program on both HP 8271 8As to establish
the communication link between the them. Enter the terminal program on both HP 82718As. Run both
programs, and type \ a
[RTN]
on one and
~.~ 0
[
RTN]
on the other. The connection will be established
when you see
%CONNECT
followed by
%OK
(or
%1
followed by
%4)
in both displays. If the connection is not
established, you will see
%NO ANS
followed by
%OK
(or
%2
followed by
%4)
in both displays. If you connect
a telephone to either HP 82718A with another piece of telephone cable, you will be able to listen to the
originate and answer tones and to the sound of data being transmitted from one modem to the other.
When the
%CONNECT
message appears, the two HP 82718As will be on-line to each other, and one can
serve as the host for the other. By configuring the host HP 8271 8A to act like the host computer you
expect to use, you can quickly begin to see what will happen when the other HP 82718A is used as a
terminal. And you have complete control of the configuration of the "host", so you can experiment to see
how the modem behaves in different circumstances.
Auto-Answer
The modem can auto-answer-that is, automatically answer incoming calls and respond to a received
originate tone with an answer tone, thus establishing a communication link with the calling computer.
The ring count distinguishes whether the modem behaves as
AUTO-ANSWER
or
ORIGINATE-ONLY.
If the
ring count is zero, the modem will report incoming rings, but not answer them
(ORIGINATE-ONLY).
If
the ring count is non-zero, the modem will answer incoming calls after
ring
count
rings
(AUTO-ANSWER).
AUTO-ANSWER
and
ORIGINATE-ONLY
apply only when the modem is in
MODEM
mode. In
VOICE
mode, the
modem only reports incoming rings, regardless of the ring count. For further details, see the description
of the
C (COUNT)
command in the IILow-Level Modem Command Dictionary".
To specify
AUTO-ANSWER,
you must put the modem in
MODEM
mode and set the ring count to a value
greater than zero. Here is a sample program:
41
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