Avago Technologies LSI8751D - Manual (Page 19)

TolerANT
®
Technology 1-5
1.3 TolerANT
®
Technology
The LSI53C875 features TolerANT technology, which includes active
negation on the SCSI drivers and input signal filtering on the SCSI
receivers. Active negation actively drives the SCSI Request,
Acknowledge, Data, and Parity signals HIGH rather than allowing them
to be passively pulled up by terminators. Active negation is enabled by
setting bit 7 in the
SCSI Test Three (STEST3) register.
TolerANT receiver technology improves data integrity in unreliable
cabling environments, where other devices would be subject to data
corruption. TolerANT receivers filter the SCSI bus signals to eliminate
unwanted transitions, without the long signal delay associated with
RC-type input filters. This improved driver and receiver technology helps
eliminate double clocking of data, the single biggest reliability issue with
SCSI operations. TolerANT technology input signal filtering is a built-in
feature of the LSI53C875 and all LSI Logic fast SCSI devices. On the
LSI53C875, the user may select a filtering period of 30 or 60 ns, with
bit 1 in the
SCSI Test Two (STEST2) register.
The benefits of TolerANT technology include increased immunity to noise
when the signal is going HIGH, better performance due to balanced duty
cycles, and improved fast SCSI transfer rates. In addition, TolerANT
SCSI devices do not cause glitches on the SCSI bus at power-up or
power-down, so other devices on the bus are also protected from data
corruption. TolerANT technology is compatible with both the Alternative
One and Alternative Two termination schemes proposed by the
American National Standards Institute.