Thursday, July 2, 2015

Touchdown calibration Specification

Touchdown calibration
Specification
Touchdown calibration is used to find maximum power to apply this to the heater element for each head on a drive
This done by applying power to heads until they maximum or allowable power has been applied
The head to media contact happens only during calibration process
The head not supposed to make contact with media in normal read-write –in order not to register this stress in the servo bias
The result of this check will be saved in 0x46 file
This check id is 0x6f

First collect all information and data necessary to the check
The estimated testing  time per head is 2 minutes
The number of testing zones is defined in 0x6f

Its sequence
1-get check data from DATA_BUFFER
2-run preamp gain calibration and 2tjog test
3-set write buffer to  zero-then do a write cylinder head sector (CHS) to collect reference information
4-??accumulate servo flex bias>>what about it?
The head gets close to the media-then head arm deviates from the track
So servo flex bias circuit increases amount of current to take head arm back to desired track 
5-save results to file id 0x96 and 0x46


But be ware that all information and storage will be final cleaned up-update test data in 0x96 and 0x46 with the maximum read/write power settings for each head/zone
Then dynamic fly height (DFH) can be executed

Input data structure
1-0x6f  

 

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