6.3.4 DASP- (Drive active/drive 1 present)
This is a time-multiplexed signal which indicates that a drive is active, or
that Drive 1 is present. This signal shall be an open collector output and
each drive shall have a 10K ohm pull-up resistor.
During power on initialization or after RESET- is negated, DASP- shall be
asserted by Drive 1 within 400 msec to indicate that Drive 1 is present.
Drive 0 shall allow up to 450 msec for Drive 1 to assert DASP-. If Drive 1
is not present, Drive 0 may assert DASP- to drive an activity LED.
DASP- shall be negated following acceptance of the first valid command by
Drive 1 or after 31 seconds, whichever comes first.
Any time after negation of DASP-, either drive may assert DASP- to indicate
that a drive is active.
NOTE 1 - Prior to the development of this standard, products were introduced
which did not time multiplex DASP-. Some used two jumpers to indicate to Drive
0 whether Drive 1 was present. If such a drive is jumpered to indicate Drive
1 is present it should work successfully with a Drive 1 which complies with this
standard. If installed as Drive 1, such a drive may not work successfully
because it may not assert DASP- for a long enough period to be recognized.
However, it would assert DASP-to indicate that the drive is active.
|
