Control Data Corporation BR8 SERIES Hardware Maintenance Manual page 29

o
SIGNAL
INPUT LINES
-WRITE ENABLE
-WRITE FAULT
RESET
-WRITE
DATA
-LOW CURRENT
-UNIT SELECT
-DOOR UNLOCK
OUTPUT LINES
-READY
-INDEX
77834769-B
TahIe 4-2. (continued)
FUNCTION
To enable the FDD write driver, this line is held at a
logic 1.
To disable the FDD write driver and enable the FDD read
circuitry, this line is held at logic
O.
500 microseconds
minimum is required after a write operation before read
data is stable.
A logic 1 level on this line clears the write fault latch.
This line contains the composite double frequency coded
write clock and data information to the FDD. The write
clock and data pulses must be 250 nanoseconds ±20% in
length and are true at the logic
1
level. Information to
be recorded on the diskette is derived from the transition
of each pulse from logic 1 to logic 0 if W2 is present, or
from logic 0 to logic 1 if W3 is present on the PWA.
This line reduces write current for tracks 43 or greater.
A low level reduces write current.
On this line a logic 1 level with W21 and W22 present or a
logic 0 level with W20 and W23 present enables the FDD
interface except for -Door Unlock and -Ready.
A logic 1 level on this line illuminates an LED indicator on
the front panel of the FDD and activates a solenoid which
unlocks the door latch mechanism, permitting manual
opening of the door.
A logic
1
level indicates that the door is closed, a diskette
is rotating, and that no write fault condition exists.
This line gives an indication of the rotational position of the
diskette by outputting a logic 1 Dulse for every index hole of
the diskette. The 1. 5 millisecond pulse is generated by
sensing the index hole in the diskette using a photo-optical
technique.
4-9