Rockwell-automation 1771-DB BASIC MODULE Bedienungsanleitung PDF herunterladen (Seite 264)

100

101

Chapter

Call Routines 69–127

13 -6

Use CALL 77 to reserve the top of RAM memory for protected variable

storage. Values are saved if you enabled CALL 74 (page13 -5).

You store values with the ST@ (page11 -35) statement and retrieve them

with the LD@ (page11 -18) statement. Each variable you store requires 6

bytes of storage space.

You must subtract 6 times the number of protected variables you are

storing from MTOP. This reduces the available RAM memory. PUSH this

value onto the stack as the new MTOP address. All appropriate variable

pointers are reconfigured. Do this only in Command mode to ensure

proper operation.

Important:

Use CALL 77 from Command mode only.

Do not let the ST@ address write over the MTOP address. This could

alter the value of a variable or string.

CALL 77 de-allocates all the string memory along with all the string

contents. Therefore, make sure you perform this call before execution

of the string statement.

Input and Output Arguments

This routine has one input argument and no output arguments. The input

argument is the new MTOP address.

Syntax

PUSH

new MTOP address

CALL

Example

PRINT MTOP

14335

PRINT MTOP-12 (2 VARIABLES TIMES 6 BYTES EACH

)

14323

PUSH 14323 (NEW MTOP ADDRESS)

CALL 77

10 K = 678 * PI

20 L = 520

25 PUSH K

30 ST@ 14335:REM STORE K IN PROTECTED AREA

40 PUSH L

50 ST@ 14329

55 REM TO RETRIEVE PROTECTED VARIABLES

CALL 77: Protected Variable

Storage

1 2 ... 259 260 261 262 263 264 265 266 267 268 269 ... 393 394

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