Seagate Barracuda ST318418N - Manual (Page 80)

70 Barracuda 36ES2 Product Manual, Rev. B
9.7.1.1 Single-ended drivers/receivers for N models
For “N” models which use single-ended drivers and receivers, typical circuits are shown in Figure 24. Termina-
tor circuits (see Note [1]) are to be enabled only when the disc drive is first or last in the daisy-chain.
Transmitter characteristics
Single-ended drives use an ANSI SCSI compatible open collector single-ended driver. This driver is capable of
sinking a current of 48 mA with a low level output voltage of 0.4 volt.
Receiver characteristics
Single-ended drives use an ANSI SCSI single-ended receiver with hysteresis gate or equivalent as a line
receiver.
Figure 24. Single-ended transmitters and receivers on N models
Notes.
[1] Part of active terminator circuits. Non-removable LSI terminators, enabled in the drive (model N only) with
jumper plug TE when it is first of last in the daisy-chain.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in ANSI Standard T10/1302D.
[4] Source of drive terminator power is an active circuit which has an input source voltage selected by jumper
plug TP. See Figure 14. Applies to N models.
[5] Interface signal levels and logical sense at the drive I/O connector for N models are defined as follows:
Vil (low-level input voltage) = 1.0 V maximum (signal true); minimum = Vss – 0.5 V.
Vih (high-level input voltage) = 1.9 V minimum (signal false); maximum = Vdd +0.5V.
Vihys (Input Hysteresis) = 425 mV minimum
See ANSI Standard T10/1302D (SPI-3) for detailed electrical specifications.
9.7.1.2 Single-ended drivers/receivers for LW models
The maximum total cable length allowed with drives using single-ended I/O driver and receiver circuits
depends on several factors. Table 16 lists the maximum lengths allowed for different configurations of drive
usage. These values are from the SPI-3 document. All device I/O lines must have equal to or less than 25 pf
capacitance to ground, measured at the beginning of the stub.
Transmitter
(or transceiver)
Line Driver
Flat
Cable
Pair
[3]
[5]
[2]
[4]
[1]
110
Ohm
[4]
[1]
110
Ohm
Receiver
Line Receiver
[2]
TP TP