Seagate Ultra 320 User Manual download pdf (Page 32)

18 Parallel SCSI Interface Product Manual, Rev. A )

Figure 3. Voltage and current definitions

Figure 4 defines the signaling sense of the voltages appearing on the – signal and + signal lines as follows:

a. The – signal terminal of the driver shall be negative with respect to the + signal terminal for an asserted

state.

b. The – signal terminal of the driver shall be positive with respect to the + signal terminal for a negated state.

Figure 4. LVD Signaling sense

Note. For a description of V

BIAS

see Section 7.3.1 of ANSI specification (SPI-5), T10/1525D.

2.3 OR-tied signals

The BSY, SEL, and RST signals shall be OR-tied. BSY and RST signals may be simultaneously driven true by

several SCSI devices. No signals other than BSY, SEL, RST, DB(P_CRCA), and DB(P1) are simultaneously

driven by two or more SCSI devices. DB(P_CRCA) and DB(P1) shall not be driven false during the ARBITRA

TION PHASE but may be driven false in other phases.

+ SIGNAL

–

– SIGNAL

– TRANSCEIVER

–

LOGICAL 1

(ASSERTED)

(TRUE)

LOGICAL 0

(NEGATED)

(FALSE)

TIME

DIFFERENTIAL BUS VOLTAGE

=(V

–

)/2 V

–

–V

BIAS

0V (OFF

)

LOGICAL 1

(ASSERTED)

(TRUE)

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Seagate Ultra 320 User Manual Page 32