SCSI Physical Characteristics
Chapter 5
Technical Reference Manual
Page 61
Model CFP2107W (Wide, Unitized SCSI-3 P-Connector)
External Terminator Power
Power to the on-board terminators is provided by the higher of the voltage
supplied at Pin #17, 18, 51, & 52, J2 or the voltage level at the 5 Volt power
input to the drive minus one diode drop. The diode prevents back flow of current
to the drive. Termination Power to external terminators can be supplied by the
drive through Pin #17, 18, 51, & 52, J2. The TERMPWR line can be
disconnected from the drive by removing Jumper E8. Table 5-11 describes the
electrical characteristics of the TERMPWR line when it is used to supply power
to an external terminator.
Table 5-15
TERMPWR Electrical Output Characteristics
Signal Characteristic
Value
Supply voltage
4.06 VDC to 4.56 VDC
(dependent on power supplied to
the drive)
Minimum source capability:
1500 mA
Table 5-16
TERMPWR Input Electrical Characteristics
Signal Characteristic
Value
Input voltage
4.00 VDC to 5.25 VDC
Minimum source capability:
1500 mA (fused at 1500 mA)
Sink current:
1.0 mA maximum, excluding
power to the internal terminator.
Internal Termination
This drive provides on-board Alternative 2 active termination for the SCSI bus.
The termination resistors, which are contained in three Single Inline Packs
(SIPs) should be removed from the drive unless it is a SCSI device at a physical
end of the bus. The terminator equivalent circuit is shown below for reference:
Figure 5-2
Terminator Equivalent Circuit
+5V
TERMPWR
F1
2.5K
10K
-DB0
-DB1
-DB2
-REQ
-I/O
: :
: :
: :
110
Voltage
Regulator
E8
