Tektronix 2714, Руководство программиста

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Programming
6–42
2714 & 2715 Programmer Manual
Next the programmer should use an algorithm similar to the following one to
accept the data entry:
H
Do
KEY?
queries until the result is not
NULL
.
H
Use appropriate error checking to ensure only numeric, decimal point, and
terminator key entries are accepted.
H
Begin building an ASCII string by appending successive key presses to a
string variable, say
VAL$
.
H
Change line 15 of the menu with this command:
DEFMENU L15:" ENTER REF LEVEL:  + VAL$ + _"
H
Loop until the whole number has been entered and a terminator has been
detected.
For example, if the keys [1] [5] [.] and [7] are pressed, the menu display will
appear as shown in Figure 6–6. When a terminator key is pressed, the program
must respond by setting the reference level using the
REF
command:
REF 15.7 DBM
CLRMENU
The
CLRMENU
command automatically exits the menu. If desired, you may
remain in the remote menu by issuing the necessary
DEFMENU
commands to
rewrite the screen.
TEST MENU
0 INIT INSTRUMENT
*1 CHANGE REF LEVEL (NOW 12.3 DBM)
2 PERFORMANCE TESTS
ENTER REF LEVEL: 15.7_
Y = +DBM Z= -DBM
Figure 6–6: Specifying a Numeric Value