Line 49 Execution jumps
to
line 20 to allow another name
to
be entered. Lines 20
through
40 form an infinite loop.
Experiment
#6
Input from the COM: device
The procedure to input from the serial port
is
quite similar, as illustrated by changing
the previous program as follows:
Enter Edit Mode and change lines 20 and 30 to
20
INPUT
#1,
N$
30
PRINT
N$
Before executing the program, make sure the peripheral device is properly connected
to the serial port and ready to transmit a string
of
characters. The string should
be
terminated with a comma or a carriage return and a line feed.
Execute this program, then have the peripheral device send a string.
If
everything is
working properly, you will see the string which was sent from the peripheral device
displayed on the Model
100.
Since the program loops back
to
the INPUT statement, you can have the peripheral
device send
as
many strings as you wish. You will have
to
press
(BREAK)
to terminate
the program.
Experiment
#7
Interrupt from the COM: device
You can interrupt execution
of
a BASIC program from the serial port. This can be
very useful to allow communications with a peripheral device which transmits data at
unpredictable times. For example, a lab instrument might send test results sporadically
as
they are completed. Using the interrupt capability, you could use the Model 100
to
run a BASIC program, yet still capture the data from the instrument whenever it
is
sent.
If
you have another terminal, such
as
another computer or a CRT terminal, you might
try the following experiment which will serve to illustrate the concept.
Clear memory with the NEW command and enter
10
OPEN
"COM:37010"
FOR
INPUT
AS
1
20
ON
COM
GOSUB
100
30
COM
ON
a0
PRINT I : 1=1+1 :
GOTO
a0
100
PRINT INPUT$
(111)
:
RETURN
Execute this program. You will see numbers starting at zero and incrementing by one
displayed along the left margin. These numbers will continue to print until a character
is received through the serial port. When this happens, the character received will also
be displayed.
If
a string of characters
is
received through the serial port they will all be displayed
before the program continues printing the numbers.
172
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