Electrical Interface For Aha-1744; Internal Connector - Adaptec AHA-1740A Technical Reference Manual

EISA-to-Fast SCSI Host Adapter

Electrical Interface for AHA-1744

As specified by ANSI X359.2/86-109 Rev. 10h for differential alternatives.
Output Signals
Each signal driven has the following output characteristics when measured at the
SCSI device's connector:
Signal
V
OL
V
OH
V
OD
V and V are measured between the output terminal and the SCSI device's logic ground
OL OH
reference.
Input Signals
SCSI inputs meet the following electrical characteristics on each signal (including
both receivers and passive drivers):
Signal
I
I
Maximum input capacitance = 25 pF.
The I requirement is met with the input voltage varying between -7 and +12 volts DC, with
I
power on or off, and with the hysteresis equaling 35 millivolts, minimum.

Internal Connector

Unshrouded 50-pin header, compatible with unshielded alternative 1 connector as
specified 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
3-M
T&B Ansley
The 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 (Z
ohms. Cable shielding is necessary if extremely noisy circuitry or extremely noise-
sensitive circuitry is present inside the host computer frame.
Definition
Low-level output voltage
High-level output voltage
Differential output voltage
Definition
Input current on either input
Model
N.A.
N.A.
Characteristics
1.7 volts DC maximum at I
output current) = 55 mA)
2.7 volts DC minimum at I
output current) = -55 mA)
1.0 volts DC minimum with with common-
mode voltage ranges from -7 to +12 volts DC
Characteristics
+/- 2.0 mA maximum
Part Number
3425-6000
609-5000M
Introduction
(low-level
OL
(high-level
OH
) of 100 +/-10
0
1-7