Rockwell Automation 9323-S5500D A.I. SERIES MICROLOGIX 1000 AND PLC-500 SOFTW - Manual (Page 506)

Error Codes
B-v
Memory Errors
Memory errors occur when your computer does not have enough random access
memory (RAM) available to accomplish an operation.
This can occur even if you have a large amount of RAM installed on your system,
because DOS applications require base memory from the first 640K. At the time DOS
was designed, 128K was a very large amount of RAM for a personal computer. If you
have more than 640K in your system, you will need to use one of the methods described
below, under Memory Beyond 640K.
DOS itself uses part (about 30K to 50K, depending on the version and configuration
options) of the base memory, as do device drivers (mouse and network drivers, for
example), memory resident programs (TSRs), and menuing software.
To operate effectively, PLC-500 A.I. requires that at least 400K of base RAM be
available after loading DOS and the other software mentioned above. You will also
need at least 3 M of Extended Memory free.
PLC-500 A.I. uses dynamic memory allocation. This means that it requests memory
from the system as it is needed. You may have enough memory free to use some
features but not others. For example, when you copy a block of rungs to the scrap
buffer, an area of memory large enough to hold those rungs is allocated. When you
clear the scrap buffer, that memory becomes available for other functions.
Checking the Amount of Memory Available
A good way to check your available memory is to run the DOS CHKDSK command (or
MEM). To run this command:
1. Get to a DOS prompt. It should look something like this:
C:\>
2. Type CHKDSK [Enter] .