NVRAM

KAS uses NVRAM to save Retain Variables.

Hardware Type

NVRAM Size Allocation

Simulator

256 Kbytes

AKD PDMM or PCMM

32 Kbytes

PCMM2G

256 Kbytes


  • Part of NVRAM allocation is reserved to store some internal data (144 bytes).
    As a consequence, not all of the complete physical NVRAM is available for the retain variables.

If the size is big enough, KAS updates the non-volatile memory to store the retain variables values.

  • This operation is performed in the background every 20 seconds.
  • The frequency increases to every two seconds when the application is running or when you shutdown the application.

NVRAM Life Expectancy

  • Data Retention: At maximum operating temperature, the data written to the memory is retained for 10 years.
  • Endurance: NVRAM memory has an endurance limit of 1014 read / write accesses.
    • More than 6,000,000 years of being accessed every 2 seconds.

  • Using the retain variables is very cycle time consuming.
    As a consequence, Kollmorgen strongly recommends to carefully monitor the system load with the TraceTimes command.

Verify the NVRAM Space

To calculate NVRAM space, add the size of each retained variable according to the:

  • Data Types
  • Arrays - The numbers of elements in case the variable is declared as an array.

Remember! Add the 144 bytes!

In this example, the total size is: 3684 bits (which is less than 0.5 Kbytes).

Variable

Size / element

Number of Element

Total Size / variable

bLedStatus

1-bit

4

4

Internal data

1152-bits (144 bytes)

N/A

1152

MasterAbsPos

64-bits

1

64

MyString

800-bits (100 bytes)

3

2400

TravelSpeed

64-bits

1

64