Freescale Semiconductor, Inc.
2.3
SHORT PASSIVE BUS OPERATION
The short passive bus is intended for use when up to eight TEs are required to communicate with
one NT. The TEs can be distributed at any point along the passive bus, the only requirement being
that the termination resistors be located at the end of the passive bus. Figure 2鈥? illustrates this wiring
configuration. CCITT I.430, ETSI ETS 300012, and ANSI T1.605 specify a maximum operational dis-
tance from the NT of 200 meters. This corresponds to the distance D2 as shown in Figure 2鈥?.
<
D2
>
TxP
NT
TR
TR
TxN
MC145574
RxP
Freescale Semiconductor, Inc...
TR
TR
RxN
TxP TxN RxP RxN
MC145574
TE
TxP TxN RxP RxN
MC145574
TE
TxP TxN RxP RxN
MC145574
TE
Figure 2鈥?. Short Passive Bus
2.4
EXTENDED PASSIVE BUS OPERATION
A wiring configuration whereby the TEs are restricted to a grouping at the far end of the cable, distant
from the NT, is shown as the 鈥淓xtended Passive Bus.鈥?This configuration is shown in Figure 2鈥?. The
termination resistors are to be positioned as shown in Figure 2鈥?.
<
D4
>
TxP
NT
TR
TR
TxN
MC145574
RxP
TR
TR
RxN
TxP TxN RxP RxN
MC145574
TE
TxP TxN RxP RxN
MC145574
TE
D3
<
>
Figure 2鈥?. Extended Passive Bus
2鈥?
MC145574
For More Information On This Product,
Go to: www.freescale.com
MOTOROLA