Scsi Bus Drivers/Receivers - Seagate ST251N Product Manual

1.12 SCSI BUS DRIVERS/RECEIVERS
The ST251 N/277N use open collector drivers. All signals are termi-
nated with 220
Q
to +5 VOC (nominal) and 330 0 to ground. The
terminating resistors are removable for multi-drive configuration.
For these measurements, SCSI bus termination is assumed to be ex-
ternal to the drive. A typical drive is supplied with the resistor termi-
nation packs installed.
Signals driven by the ST251 N/277N have the following output charac-
teristics, when measured at the drive connector:
Signal assertion
=
o.o
voe
to 0.4
voe
Minimum driver output capability
=
48 mAmps (sinking)@ 0.5
voe
Signal negation
=
2.5 VOC to 5.25 VOC
Signals received by the ST251 N/277N must have the following input
characteristics, when measured at the drive connector:
Signal true:
Maximum total input load:
Signal false:
Minimum Input Hysteresis:
o.o
voe
to 0.8
voe
-0.4 mAmps@ 0.4
voe
2.0
voe
to 5.25
voe
0.2
voe
ST251 N/277N Product Manual, Rev. B
1-13