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2-6
Theory of Operation
Signal
Drive Select
Head Load
Head Select
Low Current
Move In
Step
Write Enable
Disc Change
Disc Two-Sided
Index
Ready
Track Zero
Write Protect
Read Data
Write Data
Table 2-1.
Control, Status and Data Lines
Between the Controller and Drive Electronics
Mnemonic
DRVO-3
HEAD LOAD
HEADSEL
LOWCURR
MOVE IN
STEP
WRITDRV
DISCHNG
TWO-SIDE
INDEX
READY
TRACKO
WRPROT
RDATA
WDATA
Function
Control Signals
Identifies disc drive with which controller desires to
communicate.
Loads the heads and locks the door on the unit identified by
Drive Select.
Selects head 1 when active, head 0 otherwise.
Reduces write current on inner tracks to decrease bit shift.
Causes heads to move toward center of disc when active
during a Step command. Heads move away from center
when active during a Step command.
Causes heads to move in direction specified by MOVEIN.
Places disc drive in write mode when active.
Status Signals
Asserted when the selected drive is either not ready (due to
no disc) or has a new disc inserted.
Asserted when disc is found to be two-sided.
Asserted when index hole in disc passes photodetector.
Asserted when a disc in the selected drive has rotated for at
least two revolutions.
Asserted when heads are positioned at track zero,
Asserted when disc in selected drive is write protected.
Data Lines
Carries read data to the controller from the drive.
Carries write data to the drive from the controller.
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