Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario descargar pdf (Pagina 48)

Operating Functions

Chapter 5

5–11

5.3.11.1 RAM

When you enter RAM(cr), the BASIC Module selects the current

program from RAM MEMORY.

Important: RAM space is limited to 13 K bytes. Use the following

formula to calculate the available user RAM space:

LEN system control value which contains current RAM

program length

+# bytes allocated for strings (first value in the STRING

instruction)

+6 * each array size + 1 (asterisk = multiply)

+8 * each variable used (including each array name)

+1024

– number of bytes reserved for BASIC

Available user RAM= MTOP–V

5.3.11.2 ROM

When you enter ROM [integer], the BASIC Module selects the current

program out of EPROM memory. If no integer is typed after the

ROM command (i.e. ROM) the module defaults to ROM 1. Since the

programs are stored in sequence in EPROM, the integer following

the ROM command selects which program the user wants to run or

list. If you attempt to select a program that does not exist (e.g. you type

in ROM 8 and only 6 programs are stored in the EPROM) the

message ERROR: PROM MODE is displayed.

The module does not transfer the program from EPROM to RAM when

the ROM mode is selected. If you attempt to alter a program in

the ROM mode, by typing in a line number, the message ERROR:

PROM MODE displays. The XFER command allows you to transfer

a program from EPROM to RAM for editing purposes. You get no

error message if you attempt to edit a line of ROM program.

Important: When you transfer programs from EPROM to RAM you

lose the previous RAM contents.

Since the ROM command does NOT transfer a program to RAM, it is

possible to have different programs in ROM and RAM simultaneously.

You can move back and forth between the two modes when in

command mode. If you are in run mode you can change back and forth

using CALLS 70, 71 and 72. You can also use all of the RAM memory

for variable storage if the program is stored in EPROM. The system

control value – MTOP always refers to RAM. The system control value,

LEN, refers to the currently selected program in RAM or ROM.

5.3.11

Commands: RAM and ROM

[integer] (continued)

1 2 ... 43 44 45 46 47 48 49 50 51 52 53 ... 166 167

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