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Software Usage and Examples
string is just data, the data is transmitted over the phone line. If the string contains low-level modem
commands, the commands are not transmitted, but are processed locally.
t
t'10D
I t-U:
reads the contents of the 64-byte modem receive buffer and returns that data as a string to the
HP-75. When data arrives from the phone line, the modem places it in the receive buffer for t'lODHU
to read. When low-level commands or data from the HP-7 5 are echoed by the modem, the modem copies
the commands or data from the transmit buffer into the receive buffer for t'lOD
I
t'~$
to read. When the
modem reports a response
(BUSY, CONNECT,
etc.), it places the response into the receive buffer for
t'l 0 D I
t·~
$
to read.
Adapting Existing Programs to Use the Modem
Existing programs that perform data communications with the HP-75 are designed to work with an
HP-IL peripheral, such as the HP 82168A Acoustic Coupler or the HP 82164A HP-IL/RS-232C
Interface connected to a modem.
The modem provided in the HP 82718A is not an HP-IL data
communications peripheral; rather, it is a dedicated internal device, just as the card reader is not an
HP-IL mass storage device. Therefore, commands that deal with HP-IL peripherals cannot be used for
the modem, and loop configurations and loop protocol are irrelevant to the operation of the modem.
When changing a program that uses HP-IL peripherals to one that uses the modem, there are five areas
that need attention:
I)
Core input and output commands
2) Device-specific command syntax
3)
Status conditions
4)
Modem power
5) Additional modem features
CORE INPUT AND OUTPUT COMMANDS. Existing programs use either Et·H
I
0$ and !::Et·m
I
0 from
the HPILCMDS LEX file (which exists by itself, in the HP-75 Data Communications Pac, and in the
HP-75 I/O ROM), or Et·HEF.: and OUTPUT (in the I/O ROM only). You need to replace those core
input and output commands with t'lOD au and t"IODOUT, respectively.
Usually, this is a direct,
straightforward replacement; for example,
D$=EtH10$( II:
I
111
~ IIUt'~L, TAD#~
!::DA II ::'
SEt·m
I
0 II: 1111 , II
Ut'~L ~
LAD# II
~
D$
from the HPILCMDS LEX file, or
Et·HEF.: II: 1111
; D$
OUTPUT 11:11
11
D$
16
•
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