Memory Types - Proces-Data PD 340 Manual

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12 Appendix 1
12.1

Memory types

The PD 340 stores data in different types of memory depending on the value of a control
variable following a reset or a power failure, and the state of the write protection.
Some variables are stored in both non-volatile memory and in volatile memory. The state of
the module's Program enable switch determines whether the contents are changed in both
types of memory or only in the volatile type.
The following memory types are listed in the channel definition tables.
Read Only
PROM ReadOnly
The PROM is always write protected and can never be changed.
RAM ReadOnly
The variable is stored in RAM and is only accessible for Reading.
Read Protected Write
EEPROM RPW (Read, Protected Write)
By setting the ProgramEnable switch to ON, the contents of the EEPROM
can be changed. The contents of the EEPROM will remain unchanged during
and after a power failure.
Read Write
RAM ReadWrite
The variable can be changed instantly. After reset or a power failure, its value
is set to zero.
Read Write, Protected BackUp Write
RAM InitEEPROM
The variable is stored in both RAM and EEPROM. After a reset, the variable
is copied from EEPROM into RAM. When the variable is changed, the value
is changed in RAM. If the ProgramEnable switch is ON, the value is changed
in both RAM and EEPROM when the variable is changed.
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