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7.3.3 Signal driving conditions
(1) Signal status value
Table 7.3 shows the correspondence between the input interface signal level at the receiving end
and its logic state.
Table 7.3 Signal status
Logic state Signal level (at receiving end)
Single-ended type
True, "1", or asserted Low (0.0 to 0.8 VDC)
False, "0", negated,, or released High (2.0 to 5.25 VDC)
(2) Signal driving method
Two driving methods are available: "OR-tied" type and "non-OR-tied" type as indicated in Table
7.4.
Table 7.4 Signal driving method
Signal status Driving method
"OR-tied" type "Non-OR-tied" type
False (*1) No SCSI device drives a signal.
The signal becomes false when the
terminating resistor circuit is
biased.
A particular SCSI device drives the
signal false. Otherwise,, no SCSI
device drives the signal.
True An SCSI device drives the signal true.
*1 In this manual, the signal is said to be false if one of the following conditions is satisfied.
– The signal is actually driven by an SCSI device to become false (non-OR-tied type).
– No SCSI device is driving the signal (OR-tied type or non-OR-tied type).
In the interface operating sequence, the driving method of the BSY and RST signals which may
be driven by two or more SCSI devices simultaneously must be the "OR-tied" type. Signals
other than BSY, RST, or DBP are not driven by more than one SCSI device. Signals other than
BSY or RST can be driven by either the "OR-tied" type or "non-OR-tied" type. The DBP signal
must not be driven false in the ARBITRATION phase. For signals other than BSY or RST, both
"OR-tied" and "non-OR-tied" types can be mixed on the SCSI bus.