Figure 17. Single-Ended Transmitters And Receivers - Seagate Elite 9 Product Manual

56
11.7.3.1 Single-ended drivers/receivers
Typical single-ended driver and receiver circuits for the Elite 9 drives are
shown in Figure 17. The reference index signal (SSREF+) is terminated with
a 2.21K ohm resistor. Each ST410800N drive has a terminator resistor
located on the main circuit board. The terminator resistor is not removable;
however, you can disable the terminator by removing the jumper on J4A pins
19 and 20 (see Figure 12).
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 0.4V.
Receiver characteristics
Single-ended drives use an ANSI SCSI single-ended receiver with hyster-
esis gate or equivalent as a line receiver.
Line Driver
Transmitter
(or transceiver)
[2]

Figure 17. Single-ended transmitters and receivers

Notes:
[1] Part of active terminator circuits. Enable drive termination when it is first
or last on the daisy chain.
Interface signal levels and logical sense at the drive I/O connector are
defined as follows:
Logic level Driver output
≥ 2.5V : ≤ 5.25V ≥ 2.0V : < 5.25V
Negated (0)
≤ 0.4V : ≥ 0.0V
Asserted (1)
The difference in the voltages between input and output signals is due to
losses in the cable.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in Section
11.7.1.2.1.
[4] Source of drive terminator power is VR1 which has an input source
voltage selected by a jumper.
Elite 9 Product Manual, Rev. C
[4]
+2.85V
Flat
110
Cable
[1]
Ohm
Pair
[3]
Receiver input
≤ 0.8V : > 0.0V
Line Receiver
Receiver
[4]
+2.85V
110
[1]
Ohm
[2]