PSI-MODEMSHDSL/SERIAL
1-10
PHOENIX CONTACT
104275_en_c00
1.6.2
Line structure (daisy chain)
Figure 1-6
Line structure
A line structure (daisy chain) is a number of components that are connected in series. Using
the permanent line modem, up to 255 devices can be connected together in 2-wire opera-
tion.
Distances of over 20 km can be covered at low data rates and with good cable quality.
You can implement a line structure in which full and half duplex interfaces are used (e.g.,
RS-485 and RS-232/RS-422). In this case, however, the protocol must ensure that all in-
terfaces are operated in half duplex mode.
If a line structure is created with just full duplex-compatible interfaces (RS-232, RS-422),
the protocol must ensure half duplex mode.
RS-232 and RS-422 interfaces are usually designed for a point-to-point connection and
not a line structure.
In mixed operation with an RS-232 device and an RS-422 or RS-485 device, hardware or
software handshake is not supported.
In the case of RS-422 and RS-485, there are no cables designed for hardware hand-
shake. This is therefore not supported.
There is no defined general software handshake for RS-232, RS-422, and RS-485. This
is therefore not supported either.
RS-485
RS-485
RS-485
SHDSL
SHDSL
SHDSL
RS 232
RS 232
RS 422
RS 485
RS 232
RS 422
RS 485
Standard
Special case, half duplex
(RS-232/RS-422 and RS-485)
Table 1-2
Information on the interfaces
Interface basics
Connection to the SHDSL modem (connector pin assign-
ment)
RS-232
See "RS-232 interface" on page 2-10
RS-422
See "RS-485 W2/RS-422 interface" on page 2-11
RS-485 W2