Avago Technologies LSI53C876E - Manual (Page 48)

2-26 Functional Description
when the pins (nA) of the SN75976A are configured as inputs. When the
data pins are inputs, the resistors provide a bias voltage to both the
LSI53C876 pins (SEL/, BSY/, and RST/) and the SN75976A data pins.
Because the SEL/, BSY/, and RST/ pins on the LSI53C876 are inputs
only, this configuration allows for the SEL/, BSY/, and RST/ SCSI signals
to be asserted on the SCSI bus. The differential pairs on the SCSI bus
are reversed when connected to the SN75976A, due to the active low
nature of the SCSI bus.
The pull-up value should be no lower than the transceiver I
OL
can
tolerate, but not so high as to cause RC timing problems.
Note: Use the TI SN75976A differential transceivers to achieve
Ultra SCSI transfer rates.
8-Bit/16-Bit SCSI and the Differential Interface – In an 8-bit SCSI
bus, the SD[15:8] pins on the LSI53C876 should be pulled up with a
1.5 k
Ω
. resistor or terminated like the rest of the SCSI bus lines. This is
very important, as errors may occur during reselection if these lines are
left floating.