SLC500 CPU

[Pulsar2003 0]

Hello, Hope this will be an easy one. It's quite simple I believe. It has to do with the memory capacity of this line of CPU. The 511, 521, 531, 541, 551 all have the same amount of memory indicated the the last digit. But the second as it increases is a more powerful CPU(and more). Now when we add a memory module a 551 can basically mutate to be a 553 (for example)? Does this mean that the CPU will not see the difference? In the literature (1747-UM-011-en)guide for these CPUs from page 43 there is some explanations on the memories but it is a bit confusing mostly when it comes to the part 'Burning Program on EEPROM'. Now if your 'Burn' the program can you alter it afterwards? Thank you.

[Ken Roach 194]

SLC-500 modular controllers always have a fixed amount of memory that cannot be changed. When you add a "memory module", that is purely an EEPROM that must be sized and specified to match the CPU's model and memory. The last digit doesn't actually designate the memory size, but rather a controller model. Increasing digits designate the RAM options within that model (5/03, 5/04, 5/05, etc) rather than an absolute amount of RAM. The EEPROM are exactly what they sound like: an Electrically Eraseable Programmable Read Only Memory. When you "burn" a program to EEPROM you're backing it up to nonvolatile memory but you can still run and edit the program that remains in RAM. The EEPROM copy of the program only gets loaded into RAM under circumstances you configure: usually on program corruption, or manually when an RSLogix 500 user requests that action.