Internet PLC Forum

General => Technical support => Topic started by: PLY on July 16, 2002, 06:28:18 AM

Title: Write Memory
Post by: PLY on July 16, 2002, 06:28:18 AM

HI ! I want to write memory in arear at not clear if power OFF.Then ON power the old data not clear.

Title: Re: Write Memory
Post by: support on July 16, 2002, 08:46:33 AM

Do you mean you want to write to the non-volatile memory? You can use the SAVE_EEP command to save the data to EEPROM memory. These will not be lost after power off. When power on, read the data back using the LOAD_EEP command. There are 1700 words (16-bit) available in the M-series PLC which can be used to store non-volatile data. Note that reading and writing to EEPROM are slow and there is a fixed life cycle (about 100,000 erase/write cycles) so you should exercise necessary caution when using the EEPROM memory.

Title: Re: Write Memory
Post by: whenry on July 15, 2003, 12:09:34 PM

What constitutes a write cycle.  

1.   If I save 8 pieces of data to 8 memory locations locations using one custom function, does that constitute 8 write cycles.  

2.  Everytime A new or updated program is loaded into the PLC is that just one write cycle, or are the number of program words counted?

Title: Re: Write Memory
Post by: support on July 15, 2003, 12:36:57 PM

Write cycles is per memory location. So if you write 8 data to 8 different locations, each location only undergoes 1 write cycle.

When you transfer program to the PLC, each complete transfer is considered 1 cycle.

Anyway, the program EEPROM and data EEPROM occupies different memory locations so they are independent of each other.