DS2109DK
DS2109DK
DS2109 Demo Board
The DS2109DK is used in Plug and Play SCSI mother-
boards and host bus adapters to provide automatic
active termination for 18 pairs of signal lines and is avail-
able in a 28鈥損in SOIC package. The DS2109DK is a
demo board for both narrow and wide SCSI. A
DS21S07AE is used with the DS2109DK to terminate
27 lines for a SCSI鈥? or SCSI鈥? wide bus.
To use as a terminator for a narrow bus, connect the
SCSI cable into J2 of the DS2109DK. To use at the end
of a wide bus, connect to J1. Test points are available for
all of the SCSI bus signals. The TERM PWR LED indi-
cates termination power from the bus.
To demonstrate the automatic termination schemes of
the DS2109DK, connect cables to both J1 and J2. The
SCSI specifications require terminators installed in the
middle of the SCSI bus to be powered down or isolated
from the bus. The PDO LED will turn on when the
DS2109DK is isolated from the SCSI bus. The ground
detect method is controlled by switch GND DETECT.
Move the switch to YES, and if SCSI devices are
installed at both connectors, the PDO LED will come on.
The current sense method requires switch CURRENT
SENSE to be YES and then swtiching the RESET
switch from FLOAT to GND to FLOAT. This imitates a
SCSI reset from the host controller. If terminators are
connected to J1 and J2, the PDO LED will light. When
not demonstrating the automatic termination schemes,
leave switches S1 and S2 at NO and switch S3 at
FLOAT.
MATERIALS USED:
PART
U1
U2
J1
J2
S1鈥?
C1
C2, C4
C3, C5
L1鈥?
Z1
R1鈥?
DESCRIPTION
Plug and Play SCSI Terminator
SCSI Active Terminator
Wide SCSI connector
Narrow SCSI connector
Switch
2.2
碌F/16V
tantalum capacitor
4.7
碌F/10V
tantalum capacitor
0.1
碌F/10V
ceramic capacitor
SMT Red LED Jlead
350 mW SOT23 2.7V Zener
1/8W 5% 1.2K Resistor
SOURCE
Dallas Semiconductor
Dallas Semiconductor
Thomas and Betts
Thomas and Betts
PM Circuits Inc.
Sprague
Kemet
Kemet
Digikey
Digikey
MEPCO
PART NUMBER
DS2109S
DS21S07AE
HFR068RA29BS1
501鈥?007ES
D7789
293鈥揦225X9010A2T
T491A475K010AS
C1206C103K5RAC
P500
BZX84C2V7ZX
9C12063A1201JKR
022698 1/3
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