Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario descargar pdf (Pagina 160)

Error Messages and

Anomalies

Chapter 9

9–8

2. When

using the variable I before an ELSE statement, put a space between

the I and the ELSE statement. If you do not, the program assumes that

the IE portion of IELSE is the special function operator IE.

This error may or may not yield a BAD SYNTAX — IN LINE XXX

error message, depending on the particular program in which it is

used.

Examples:

Wrong

u20 IF I u10 THEN PRINT IELSE 100

uLIST

20 IF I u10 THEN PRINT I ELSE 100

Right

u20 IF Iu10 THEN PRINT I ELSE 100

uLIST

20 IF I u10 THEN PRINT I ELSE 100

3. Do not place a space character inside the ASC() operator. A statement

ASC() yields a BAD SYNT

AX ERROR. Y

ou can put spaces

strings, however

, allowing the following statement to work properly:

LET $(1) u“HELLO, HOW ARE YOU”

ASC() yields an error because the module eliminates all spaces when

a line is processed. ASC() is stored as ASC() and the module

interprets this as an error.

4. Do not use the following one letter variables: B, F, R. Unpredictable

operation could result.

5. Do

not use the following two letter variables: CR, DO, lE, IF

, IP

, ON, PI,

SP, TO, UI and UO.

6. When

using an INPUT statement to enter data you must be sure to enter

valid data. If you enter invalid data you see the prompt “TR

Y AGAIN”.

This disrupts the screen layout.

7. SQR(M–M2) gives a bad argument if M=O.

8. ONTIME does not interrupt CALL routines, INPUT statements or

PRINT# statements waiting for handshaking (XON, CTS, DCD) to

become true. ONTIME is a polling mechanism which is checked after

each line of BASIC is completed. End of line is either a (CR) or (:).

9.4

Anomalies (continued)

1 2 ... 155 156 157 158 159 160 161 162 163 164 165 166 167

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