Modem Specifications; Runaway Transmitter Recovery - Siemens SIMATIC TI505 Installation And Operation Manual

Modem Interface Ports (continued)
Modem
Specifications
Runaway
Transmitter
Recovery
3-6 TIWAY I Network Communication
The line drivers and receivers meet the requirements for the RS-423 and
RS-232-C standards. The modem interface is user-selected for either
asynchronous or synchronous operation at data rates of 110, 150, 300, 600,
1200, 2400, 4800, 9600, 19.2K, 38.4K, 57.6K, and 115.2K bits per second.
For communication applications longer than the 25,000 feet limit of the
Local Line interface, you need to use modems.
The modems used must be non-intelligent and have data transparency.
Non-intelligent refers to the class of modems that do not have an internal
command set. Modems such as the Hayes Smartmodem and compatibles
do have an internal command set and should not be used. (Generally,
modems that meet the Bell 103, 202, and 208 specifications will work, but
the Bell 212A class modems will not.) In addition to being non-intelligent,
the modems must support data transparency, which means no start bits, no
stop bits, and no parity. This is necessary because TIWAY I uses the
bit-oriented HDLC protocol to transfer information between devices. Most
short-haul modems are non-intelligent and provide data transparency.
You also have a choice of using either NRZ or NRZI encoding with the
modem interface. NRZI is recommended because of its self-clocking
properties. (Please refer to the appropriate TIWAY documentation for
specific details regarding the use of modems.)
The S5 UniLink Adapter is equipped with a timeout or runaway transmitter
recovery mechanism which ensures that the transmitter does not remain
turned on longer that twice the time required to send the maximum length
message. If the transmission exceeds this limit, the Adapter will perform a
hardware reset, discarding all macro buffers and any outstanding
directives.
NOTE: The hardware reset restores the UniLink Adapter to the initialized
or power-up state. At this point, the Adapter will have to be reconfigured
and the network restored to its operating state.
S5 UniLink Adapter Installation and Operation