Interface Cable Requirements - Seagate MEDALIST 1080SL Product Manual

Medalist 1080sl SCSI Product Manual, August 1995
Signal
Signal name pin number
ATN– 32
Ground 33–34
BSY– 36
ACK– 38
RST– 40
MSG– 42
SEL– 44
C/D– 46
REQ– 48
I/O– 50
Caution. Do not connect pin 25 to ground. If you plug in the connector
upside down, the terminator power on pin 26 is shorted to
ground. This may damage the drive.

2.5 Interface cable requirements

A characteristic impedance of 100 ohms +10% is recommended for the
unshielded flat or twisted-pair interface cable. However, most available
cables have a somewhat lower characteristic impedance. To minimize
discontinuities and signal reflections, do not use cables of different
impedances in the same bus. Implementation may require tradeoffs in
wielding effectiveness, cable length, the number of loads and the transfer
rates to achieve satisfactory system operation. If shielded and un-
shielded cables are mixed within the same bus, the effect of impedance
mismatch must be carefully considered. This is especially important for
maintaining adequate margin for Fast SCSI transfer rates.
19
Ground
pin number
31
—
35
37
39
41
43
45
47
49