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When password protection is enabled, the user password you set in your instrument should
be written into the device authorization register (2575) before another write request is
issued. If the correct password is not supplied while password protection is enabled, the
instrument will respond to all write requests with the exception code 01 (illegal operation).
It is recommended to clear the password register after you have completed your changes in
order to activate password protection.
2.9 Data Recording and File Transfers
2.9.1 Log File Organization
Historical files are stored to the non-volatile memory with a battery backup. Memory is
allocated for each file statically when you set up your files and will not change unless you
re-organize the files. The PM174 automatically performs de-fragmentation of the memory
each time you re-organize your files. This helps keep all free memory in one continuous
chunk and thus prevents possible leakage of memory caused by fragmentation.
Data records in a file are arranged in the order of their recording. Each record has a unique
16-bit sequence number that is incremented modulo 65536 with each new record. The
sequence number can be used to point to a particular record in the file, or to check the
sequence of records when uploading files from the device.
Each file has a write position pointer that indicates the place where the next record will be
recorded, and a read position pointer that indicates the place from where the current record
will be read. Both pointers show sequence numbers of the records they point to rather than
record offsets in the file.
After acknowledging a record you have read, the read pointer automatically advances to the
next record in the file. When the read pointer gets to the record to which the file write
pointer points, the end-of-file (EOF) flag is set. It is automatically cleared when a new
record is added to the file, or when you explicitly move the read pointer to any record
within a file.
If a file has a wrap-around attribute (circular file), the most recent records can overwrite
the oldest records. When this happens at the current read position, the read pointer
automatically advances forward in order to point to the oldest record in the file.
The PM174 keeps a separate read pointer for each communication port so that access to the
same file through a different port will not affect current active sessions for other ports.
Multi-section Files
Log files can have one or more (up to 16) sections for multi-channel recording. An ordinal
file consists of a single section. Some files, such as daily profile log files and waveform log
files, are arranged as multi-section files.
A multi-section file is subdivided into multiple sections of the same structure, one section
per recording channel. The number of sections in each file is defined at the time you set up
your files and may not change unless you re-organize the file. Each section within a multi-
section file can be addressed by a section number, or by a section channel ID.
A multi-section file has a single write position pointer for all sections and stores data in all
sections simultaneously. This means that records with the same sequence number in all
sections are associated with the same event. A multi-section file has also a single read
position pointer for all sections.
Data Log Files
Data log files can store up to 16 measured parameters per a record. Any data measured by
the device can be stored in the log file. The number of parameters that each record will hold
and the list of parameters you want to be recorded in the file can be selected through the
Data log setup registers for a particular file.
Recording data to the data log files can be triggered through the setpoints, either on a time
basis using the meter clock or periodic timers, or upon any event detected by the setpoints.
