This memory will save data even when the display unit is OFF.
The backup SRAM's user area is used to save not only the Alarm History data but also the sampling data, internal device backup data, and filing data.
The capacity of the backup SRAM that can be used for Alarm History data depends on the type of display unit and the space used by other data.
Backup SRAM has the following usage priorities:
Operation Log
Alarm History Data
Sampled Data
Backup data in internal devices
Filing Data
The Alarm History data stored in the backup SRAM is erased when:
Transferring a Screen
Memory is reset (Offline Mode)
Backup SRAM is initialized (Offline Mode)
When using GP-4100 series, the frequency at which alarm history data is saved to user memory is defined in the [Common Settings] menu's [Alarm] editor, [Storage Frequency] field.
19.10.2.4 Show History - Item/Extended
Space Requirements for Alarm History Data
The space on the backup SRAM required for saving the Alarm History data depends on the number of [Records] of all blocks and the number of registered messages (addresses).
When no message is registered, the data size is 0 bytes, regardless of the [Backup History] setting.
Calculation
Size of the Alarm History data (all blocks) (Unit: byte)
|
576 + [Number of records of Block 1 x (28 + 4 + (Number of addresses + 15)/16 x 4 + Number of addresses x 4)] ... (Apply the same calculation as Block 1 for Blocks 2 to 7) + [Number of records of Block 8 x (28 + 4 + (Number of addresses + 15)/16 x 4 + Number of addresses x 4)] + (16 x Number of registered messages) + (4 x Number of registered messages) + (4 x Number of registered messages)] |
Calculation Examples
|
Setting |
Description |
|
Setting for Block 1 |
- |
|
Data Size of Alarms for Block 1 |
768 |
|
Number of Addresses for Block 1 |
0 |
|
Settings for Blocks 2 - 8 |
None |
|
Number of registered messages |
2048 |
|
Backup setting |
- |
|
Backup Alarm History |
Enable |
Calculation Result: (576) + (768 x (28 + 0)) + (16 x 2048) + (4 x 2048) + (4 x 2048) = 71232 bytes (approximately 69 KB)