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Cheetah 36LP Product Manual, Rev. B
Notes [ ] for Tables 13 through 16.
[1]
See Section 9.6.4.1 for detailed electrical characteristics of these signals.
[2]
The conductor number refers to the conductor position when using 0.025-inch (0.635 mm) centerline flat
ribbon cable. Other cables types may be used to implement equivalent contact assignments.
[3]
Connector contacts are on 0.050 inch (1.27 mm) centers.
[4]
Front panel LED signal; indicates drive activity for host front panel hard drive activity indicator.
[5]
Asserted by host to enable Motor Start option (enables starting motor via SCSI bus command).
[6]
Asserted by host to enable Delayed Motor Start option (motor starts at power on or after a delay of 12 sec-
onds times drive ID). This and [3] above are mutually exclusive options.
[7]
Binary code on A3, A2, A1 and A0 asserted by host to set up SCSI bus ID in drive.
[8]
GND provides a means for differential devices to detect the presence of a single ended device on the bus.
Drive will not operate I/O bus at Ultra2 or Ultra3 SCSI data rates if this is grounded.
[9]
Signals [4] through [7] are used in place of installing jumpers and cables on option select connectors J2
and J6. See Section 8.1.1 notes.
[10] "NC" means no connection.
[11] 8 bit devices which are connected to the 16 data bit LVD I/O shall leave the following signals open: –DB8,
–DB9, –DB10, –DB11, –DB12, –DB13, –DB14, –DB15, and –DBP1.
8 bit devices which are connected to the 16 data bit single-ended (SE) I/O shall have the following signals
open: DB8, –DB9, –DB10, –DB11, –DB12, –DB13, –DB14, –DB15, and –DBP1.
All other signals should be connected as shown.
9.7
Electrical description
Cheetah 36LP drives are multimode devices. That is, their I/O circuits can operate as either single-ended or
low voltage differential drivers/receivers (selectable using the I/O DIFFSNS line).
See ANSI Standard T10/1302D for details electrical specifications.
9.7.1
Multimode—SE and LVD alternatives
When the interface DIFFSNS line is between +0.35 V and +0.5 V, the drive interface circuits operate single-
ended and up to and including 20 M transfers/s (Fast-20 or Ultra 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/s
or less (Fast-40 or Ultra160 SCSI).
This multimode design does not allow dynamically changing transmission modes. Drives must operate only in
the mode for which the installation and interface cabling is designed. Multimode I/O circuits used by these
drives 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 ANSI SPI-3 specification T10/1302D).
Multimode signals
Multimode circuit SE alternative signal characteristics are the same as described elsewhere in Section 9.7.1.
The SE alternative for these circuits is selected as described above. SE cables and termination must be used.
LC, LCV, LW, and LWV 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 signal (V
) driven by LVD interface drivers shall have the following output characteristics when measured
s
at the disc drive connector:
Steady state Low level output voltage* = –.95 V = < V
Steady state High level output voltage* = –.95 V = < V
Differential voltage = +0.6 V minimum with common-mode voltage ranges 0.700 V = < V
*These voltages shall be measured between the output terminal and the SCSI device's logic ground reference.
= < –1.55 V (signal negation/logic 0)
s
= < 1.55 V (signal assertion/logic 1)
s
63
= < 1.800 V
cm
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