Seagate ST251 - DC-Unsafe Option: JP2; Precompensation; Life-Test

The latched operation has two configurations which are provided at
the J7 shunt, pins
5-6.
1. No jumper at J7: The Write Fault signal can only be cleared by a
power on/off cycle. Use of this option in conjuction with the DC-
Unsafe option is not recommended.
2. Pins 5-6 shorted at J7: The Write Fault signal can be cleared by
de-selecting the
drive. When the drive is deselected, and the fault
condition is corrected, the Write Fault
signal will be false.
2.4 DC-UNSAFE OPTION: JP2
JP2 has two jumper pads, and when a jumper is installed, a DC-unsafe
condition will cause a Write Fault to be sent to the interface. Use
Fig-
ure 7 on page 2-1 to locate JP2.
2.5 PRECOMPENSATION
The ST251/251R/277R do not require precompensation.
2.6 LIFE-TEST
This is a test function used during the manufacturing process and is
not recommended
for field use. When pins 7-8 of J7 are shorted, the
stepper
motor will continuously seek between Track 0 and the maxi-
mum cylinder and will ignore control signals sent via the interface.
ST251/251 R/277R Product Manual, Rev.A
2-3