Seagate Barracuda 18XL ST318416N, Руководство по эксплуатации продукта

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80 Barracuda 18XL Product Manual, Rev. A
See ANSI Standard T10/1302D (SPI-3) for detailed electrical specifications.
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 “DIFFSNS” is between
+0.7 V and +1.9 V, the drive interface circuits operate low voltage differential and up to and including 80 M
transfers/sec or less. This arrangement is not intended to allow dynamically changing transmission modes, but
rather to prevent incompatible devices from attempting to interoperate. 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 dif-
ferential 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-3 specification T10/1302D).
Multimode signals
Multimode circuit SE alternative logic sense and signal level characteristics are described 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
Multimode circuit LVD alternative signal characteristics are not the same as high voltage differential signals
(HVD). This drive does not support HVD. It should never be connected to an HVD bus. The SCA-2, 80-pin con-
nector signal/pin assignments are shown in Tables 13b and 13d, but the electrical characteristics of the signals
are not the same. “LC” and “LW” model drives do not have onboard terminators. The Multimode signal lines
(either SE or LVD) should be terminated with 110 ohm active terminator circuits at each end of the total cable.
Termination of the I/O lines must be provided for by the Host equipment designers or end users.
The SE and differential alternatives are mutually exclusive.
Output characteristics
Each LVD signal (V
s
) driven by LVD interface drivers shall have output characteristics as described in this sec-
tion when measured at the disc drive connector (refer to figure 13). A signal that is “released” goes to the
negated (false or logic 0) state because the bias of the terminator pulls the signal levels to the negated state.
Refer to paragraphs 7.2.2, and Annex A of ANSI SPI-3 specification, T10/1302D for details. The output charac-
teristics shall additionally conform to EIA RS-485.
[1] The test circuit (figure 13) is approximately equivalent to two terminators creating the normal system bias.
Table 14: Drive steady state limits and conditions (T10/1302D, Annex A, Table A.2)
Test parameter V
S
Test conditions (figure 13) Minimum (mV) Maximum (mV)
| V
A
| Differential output voltage
magnitude (asserted) [1]
V
1
=1.056 V, V
2
=0.634 V 375 800
V
1
=1.866 V, V
2
=1.444 V 375 800
| V
N
| Differential output voltage
magnitude (negated) [1]
V
1
=1.056 V, V
2
=1.444 V 375 800
V
1
=1.866 V, V
2
=1.444 V 375 800
| V
A
| Differential output voltage
magnitude (asserted)
All four above conditions 0,69 x | V
N
| + 50 1,45 x | V
N
| – 65