AMD
S a m p le Va lu e s
Using RG-58A/U, 50 Ω coaxial cable, a successful TAXI link was established using the
following component values:
R1 = 68 Ω
R2 = 200 Ω
RE = 300 Ω
C
= 0.1 µF
5 .7 In t e rfa c in g t o Tw is t e d -P a ir Ca b le
Another low cost alternative twisted pair cable. Twisted pair cable is generally more
lossy than coaxial cable making it suitable only for short distances. To reduce the
possibility of noise being induced along the line, the shielded twisted-pair cable is
recommended.
Using the TAXlchip set with shielded-twisted-pair as the serial medium is very similar to
using it with coaxial cable. The recommended configuration is shown in Figure 5-11,
where each of the components that make up the interface serve the same purpose as in
the AC-coupled TAXl-fiber optic interface shown in Figure 5-9.
Note that with shielded-twisted-pair, only one cable is required to form the link. The
twisted-pair conductors carry the differential pseudo-ECL signals and the shield is
grounded at the Receiver.
Fig u re 5 -1 1 S h ie ld e d -Tw is t e d P a ir Ca b le In t e rfa c e
+5 V
R1
+5 V
TAXI
TAXI
RX
R1
R2
L, Z0
TX
C
C
+
–
+
–
RE
R2
RE
R1R2
= Z0/2
R1+ R2
12330E-18
5R2
Midpoint of Pseudo
ECL Signal Swing
=
= 3.7 V
R1+ R2
186 ≤ RE ≤ 7.2 (Z0)
C = Largest RF Capacitor Available
70
TAXIchip Integrated Circuits Technical Manual
AMD [ AMD ]
