Scsi Interface; Electrical Interface For Aha-1740A/1742A - Adaptec AHA-1740A Technical Reference Manual

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SCSI Interface

Electrical Interface for AHA-1740A/1742A

As specified by ANSI X3.131-1986 for single-ended operation.
Output Signals
All signals use open collector or three-state drivers. Each signal driven by a SCSI de-
vice has the following output characteristics when measured at the SCSI device's
connector:
Signal
V
OL
V
OH
Input Signals
SCSI inputs meet the following electrical characteristics on each signal (including
both receivers and passive drivers):
Signal
V
IL
V
IH
I
IL
I
IH
Minimum input hysteresis = 0.2 volts DC.
Maximum input capacitance = 25 pF (measured at the device connector closest to the stub, if
any, within the device).
1- 6
Definition
Low-level output voltage
High-level output voltage
Definition
Low-level input voltage
High-level input voltage
Low-level input current
High-level input current
AHA-1740A/1742A/1744
Characteristics
0.0 to 0.5 volts DC at 48 mA sinking (signal
assertion)
2.5 to 5.25 volts DC (signal negation)
Characteristics
0.0 to 0.8 volts DC (signal true)
2.0 to 5.25 volts DC (signal false)
-0.4 to 0.0 mA at V = 0.5 volts DC
1
0.0 to 0.1 mA at V = 2.7 volts DC
1