Fujitsu M2361A Customer Engineering Manual page 99

e. Fault Clear (Bus 4)
This signal clears the fault status i.e., Write/Read Check Status,
however, if the cause of the Fault condition still exists, the status
will flot be cleared.
See Figure 4.5.16.
f.
AM Enable (Bus 5)
AM Enable, in conjunction with Write Gate or Read Gate, is used in a
Variable Sector Format. When AM Enable is true while Write Gate is
true, an AM of three bytes (DC erase) is written on the track.
Refer to Figure 4.5.17.
When AM Enable is true whi Ie Read Ga te is true. the read c i rcui t searches
for an AM of three bytes. When the AM is found. the drive will issue
Address Mark Found to the controller.
See Figure 4.5.18.
g. RTZ (Bus 6)
Wherever the heads are located. they return to cylinder zero and head
zero when the RTZ signal is received. This signal clears the Seek Error.
Refer to Figure 4.5.19.
h. Release (Bus 9); Dual Channel only
After the drive is reserved by Unit Select or Priority Select,
Release command becomes valid at Tag 3 and Bus 9. Enabling this
signal will release the reserved status in the drive, making
alternate channel access possible after selection by the other
channel. {Refer to Figures 4.5.29 and 4.5.30.}
If the drive has been reserved by Uni t Select and the Release Timer Swi tch
on the display panel PCB (B17B-0270-0010A#U) is set to RLTM side, the
drive will automatically release the reserved condi tion approximately
500 ms after the Uni t Select command is issued.
(6) Priority Select (Bus 9 with Unit
Sele~t
Tag and Unit Select 1, 2, 4)
By sending Priority Select (Bus 9) along with Unit Select Tag, Unit Select
1, 2, 4, a controller can select the drive even if it has been selected or
reserved by the other channel, except when its own channel is disabled by
the Disable switch or the drive is priority selected by the other channel.
With this command, the drive is set in the unconditionally reserved state
with respect to that channel. Once it is unconditionally reserved, the
control becomes exclusive, i.e., the other channel cannot access the drive
until the drive is released from the controller which has reserved the
drive. If the drive is unconditionally reserved, all the signals
including Unit Selected, and Busy signals are inhibited with respect to
the other channel. (Refer to Figure 4.5.30).
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