Avago Technologies LSI53C876E - Manual (Page 50)

2-28 Functional Description
Figure 2.5 LSI53C876 Differential Wiring Diagram (Cont.)
2.2.7.2 Terminator Networks
The terminator networks provide the biasing needed to pull signals to an
inactive voltage level, and to match the impedance seen at the end of
the cable with the characteristic impedance of the cable. Terminators
must be installed at the extreme ends of the SCSI chain, and only at the
ends. No system should ever have more or less than two terminators
installed and active. SCSI host adapters should provide a means of
accommodating terminators. There should be a means of disabling
termination.
SE cables can use a 220
Ω
pull-up to the terminator power supply
(Term Power) line and a 330
Ω
pull-down to ground. Because of the
high-performance nature of the LSI53C876, regulated (or active)
termination is recommended.
Figure 2.6 shows a Unitrode active
terminator. For additional information, refer to the SCSI-2 Specification.
TolerANT technology active negation can be used with either termination
network.
SDIRP0/1
SDIR15
SDIR14
SDIR13
SDIR12
SDIR11
SDIR10
SDIR9
SDIR8
SDP1/
SD15/
SD14/
SD13/
SD12/
SD11/
SD10/
SD9/
SD8/
SD8/
SD9/
SD15/
SDP1/
SDIR8
SDIR9
1A
1DE/RE
2A
2DE/RE
3A
3DE/RE
4A
4DE/RE
5A
5DE/RE
6A
6DE/RE
7A
7DE/RE
8A
8DE/RE
9A
9DE/RE
CDE0
CDE1
CDE2
BSR
CRE
1B+
1B-
2B+
2B-
3B+
3B-
4B+
4B-
5B+
5B-
6B+
6B-
7B+
7B-
8B+
8B-
9B+
9B-
-DB0 (4)
+DB0 (3)
-DB1 (6)
+DB1 (5)
-DB2 (8)
+DB2 (7)
-DB3 (10)
+DB3 (9)
-DB4 (12)
+DB4 (11)
-DB5 (14)
+DB5 (13)
-DB6 (16)
+DB6 (15)
-DB7 (18)
+DB7 (17)
-DBP (20)
+DBP (19)
LSI538760
DIFFSENS
VDD
1.5 K
Ω
SN75976A #3
SD10/
SD11/
SDIR10
SD12/
SD13/
SD14/
SDIR11
SDIR12
SDIR13
SDIR14
SDIR15
SDIRP1
DIFFSENS DIFFSENS
(Cont.)
To SCSI
BUS