Campbell Scientific SM192/SM716 Storage Modules - Manual (Page 19)

SECTION 5. DATA RETRIEVAL
5-3
Complete details on the operation of SMCOM
are contained in the PC208 manual.
When using a computer other than an IBM
PC/XT/AT/PS-2 or compatible, the SM232A
is the recommended interface. It has a
manually operated switch to raise the
Storage Module's PE and CLK/HS lines.
Thus the user's program doesn't need to
raise pins 4 and 20 on the computer (as is
necessary with the SC532 Interface). With
the SM232A and a commercially available
terminal emulator program the user may
manually execute the telecommunications
commands to retrieve data to disk.
However, when this method is used to
retrieve large data files, there is a risk of
overrunning the computer's input buffer and
losing data. To prevent this, the user can do
one of the following.
1. Select a terminal emulator program which
has X-ON, X-OFF capability.
2. Use the C, D or F command to have the
Storage Module send the data in blocks
small enough to avoid this problem.
3. Write a program which requests the data
in blocks small enough to avoid the
problem.
4. Select a baud rate slow enough for the
computer to keep up with the data.
5.3 DATA RETRIEVAL STEPS
5.3.1 IBM PC/XT/AT/PS-2'S AND COMPATIBLES
a. With IBM PC/XT/AT's and compatibles, use
either the PC201, SC532 or SM232A. The
IBM PS-2 will not accept the PC201 Card
but is compatible with the SC532.
b. Make the appropriate connections (Section
5.1).
c. Execute SMCOM (PC208 manual).
5.3.2 NON-IBM COMPATIBLES
The following instructions apply to a
configuration using a terminal emulator program
and the SM232A. It is assumed for this example
that the terminal emulator software has X-ON, X-
OFF capability.
1. Make the connections between the
SM232A and the computer/terminal as
shown in 5.1-4. Refer to the SM232A
Instruction Manual for further details.
Enable X-ON, X-OFF in the terminal
emulator.
2. Place the toggle switch on the SM232A
in the TRANSPARENT position. This
switch should be left in this position until
the Data Terminal Ready (DTR) line of
the terminal/computer is raised high. In
the case of a terminal, this happens
when the terminal is powered,
connected to the SM232A, and set to
receive 8-bit (plus 1 start / 1 stop bit)
data at a valid baud rate. In a computer,
executing a terminal emulator program
drives DTR high under software control.
3. Once DTR is high, move the switch from
TRANSPARENT to UNLOAD (raising
CLK/HS and enabling PE), which
activates the Storage Module.
4. Send several carriage returns to
synchronize baud rates and receive the
Storage Module prompt: CR, LF, %.
5. Type in the appropriate
telecommunication commands
(Appendix D) to collect the desired data
file(s). (Prior to sending the last carriage
return to execute the C, D, or F
command, place the terminal emulator
in the receive a file mode.)
The telecommunications commands are
used here to:
a. Position the DLP (Display Location
Pointer) at the desired beginning
point of the data transfer (one of the
G commands).
b. Collect the desired file(s) using the C,
D, or F command.