Multimode-Se Or Lvd Alternative; Figure 23. Single-Ended Transmitters And Receivers - Seagate ST34520N - Medalist 4.55 GB Hard Drive Product Manual

Medalist Pro Product Manual, Rev. D
Receiver characteristics
Single-ended drives use an ANSI SCSI single-ended receiver with hysteresis gate or equivalent as a line
receiver.
Line Driver
Transmitter
(or transceiver)
[2]
Figure 23. Single-ended transmitters and receivers
Notes.
[1] Part of active terminator circuits. Non-removable LSI terminators, enabled in the drive (models "N" and
"W" only) with jumper plug TE when it is first or last in the daisy chain. Interface signals levels and logical
sense at the drive I/O connector are defined as follows:
Logic level
NEGATED (0)
ASSERTED (1)
The difference in the voltages between input and output signals is due to the losses in the cable.
[2] ANSI SCSI compatible circuits.
[3] Total interface cable length should not exceed that specified in Section 9.6.3.1.
[4] Source of drive terminator power is an active circuit which has an input source voltage selected by jumper
plug TP. See Figure 12. Applies to "N" and "W" models.
9.7.2 Multimode—SE or LVD alternative
"LW" and "LC" models have I/O circuits that can operate either in single-ended (SE) or low voltage differential
mode (LVD). When the interface "DIFFSNS" line is between 0 V and .6 V, the drive interface circuits operate
single-ended and up to and including 20 M transfers/s (Fast-20 or Ultra-1 SCSI). When "DIFFSENS" is betwen
+0.7 V and +1.9 V, the drive interface circuits operate low voltage differential and up to and including 40 M
transfers/s or less (Fast-40 or Ultra-2 SCSI). This arrangement is not intended to allow dynamically changing
transmission modes, but rather to prevent incompatible devices from attempting to interoperate. Drives must
operate only in the mode for which the installation and interface cabling is designed. Multimode I/O circuits
used by "LC" and "LW" devices do not operate at high voltage differential levels and should never be exposed
to high voltage differential environments unless the common mode voltages in the environment are controlled
to safe levels for single-ended and low voltage differential devices (see the ANSI SPI-2 specification X3T10/
1142D).
Multimode signals
Multimode circuit SE alternative signal characteristics are the same as described in Section 9.7.1. The SE
alternative for these circuits is selected as described above. SE cables and termination must be used.
Multimode circuit LVD alternative signal characteristics are not the same as the differential signals described in
Section 9.7.2.1. The Multimode signal lines (either SE or LVD) should be terminated with 110 ohm active termi-
nator circuits at each end of the total cable. Termination of the I/O lines must be provided for by the Host equip-
ment designers or end users.
The SE and differential alternatives are mutually exclusive.
TP
[4]
Flat
110
Cable
[1]
Ohm
Pair
[3]
Driver output
>2.5 V: <5.25 V
<0.4 V: >0.0 V
Line Receiver
TP
Receiver
[4]
110
[1]
Ohm
Receiver input
>2.0 V: <5.25 V
<0.8 V: >0. 0 V
71
[2]