Electrical Interface for AHA-1744As specified by ANSI X359.2/86-109 Rev. 10h for differential alternatives.Output SignalsEach signal driven has the following output characteristics when measured at theSCSI device’s connector:Signal Definition CharacteristicsVOL Low-level output voltage 1.7 volts DC maximum at IOL (low-leveloutput current) = 55 mA)VOH High-level output voltage 2.7 volts DC minimum at IOH (high-leveloutput current) = -55 mA)VOD Differential output voltage 1.0 volts DC minimum with with common-mode voltage ranges from -7 to +12 volts DCVOL and VOH are measured between the output terminal and the SCSI device’s logic groundreference.Input SignalsSCSI inputs meet the following electrical characteristics on each signal (includingboth receivers and passive drivers):Signal Definition CharacteristicsII Input current on either input +/- 2.0 mA maximumMaximum input capacitance = 25 pF.The I I requirement is met with the input voltage varying between -7 and +12 volts DC, withpower on or off, and with the hysteresis equaling 35 millivolts, minimum.Internal ConnectorUnshrouded 50-pin header, compatible with unshielded alternative 1 connector asspecified in ANSI X3.131-1986 (Figure 4-1).For connector pin out and drawing of the connector, see Appendix B.Partial list of compatible connector plugs (for reference only):Manufacturer Model Part Number3-M N.A. 3425-6000T&B Ansley N.A. 609-5000MThe cable for the internal SCSI connector should be good quality 50-conductor flat ca-ble with 26- or 28-gauge conductors and a characteristic impedance (Z0) of 100 +/-10ohms. Cable shielding is necessary if extremely noisy circuitry or extremely noise-sensitive circuitry is present inside the host computer frame.EISA-to-Fast SCSI Host Adapter Introduction1-7
