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1.3.3 SCSI Activity LED Interface
1-4
The SCSI interfaces on the LSI22910 operate as two 16-bit, synchronous
or asynchronous, SE or LVD, and support Ultra2 SCSI protocols and
16-bit arbitration. The interface is made through connectors J2 and J5 for
Channel A and J3 and J4 for Channel B. Connectors J2 and J3 are
68-pin VHDCI right-angle receptacles that protrude throughout the
ISA/EISA bracket. Connectors J4 and J5 are 68-pin high density latching
right-angle receptacles for internal SCSI connections. See
page 2-5
for the location of these connectors.
The LSI22910 provides autosensing, dual mode SE/LVD SCSI
termination. Termination is normally enabled. When a SCSI device is
sensed to be connected to both internal and external connectors,
termination for that channel is automatically disabled.
The LSI22910 supplies SCSI bus TERMPWR through a blocking diode
and self-resetting 1.5 A short circuit protection device. An on-board LED
lights up when TERMPWR is shorted and turns off.
A 40 MHz oscillator is installed on the LSI22910 board to provide the
clock frequency to the LSI53C896 that is necessary to support Wide
Ultra2 SCSI transfers of up to 80 Mbytes/s.
The LSI22910 LED interface is a four-wire arrangement that allows you
to connect an LED harness to the board. The connector on the LSI22910
is J6 for both channels. See
and pin numbers for this LED interface.
Four individual LEDs per channel are on the LSI22910 so you can
decode the operating state of the board. The four activity LEDs are:
•
SCSI Activity – Green LED, right edge of board
•
TERMPWR SHORTED – Yellow LED, right edge of board
•
LVD Mode – Green LED, right edge of board in LVD Mode
•
TERMPWR GOOD – Green LED, right edge of board when
TERMPWR is above + 3 V
Using the LSI22910
Table A.5
on
page A-9
Figure 2.1
on
for the signal name
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