Serial Port and Serial Communications
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Serial port of the DS has two modes of operation:
Data routing mode. Incoming serial data is routed to the Ethernet port and Ethernet data is routed to the serial port. It is in this mode that the DS performs its routing function. After the powerup the DS is running in the data routing mode.
Serial programming mode. In this mode the serial port is used for serial programming and all data received into the serial port is interpreted as programming commands.
Data connection with the network host can still be established and maintained while in the serial programming mode but the data received from the network host will be discarded and the data received into the serial port will be interpreted as commands. Therefore, data exchange with the network host and serial programming cannot be concurrent. DS can only perform one of the two at any given time. This is different from the network programming that can be performed concurrently with the data routing.
Operation of the serial port in the data routing mode is governed by several settings (see below), some of which (baudrate, parity, etc.) have corresponding parameters. These parameters are delivered to the DS via the network Parameter (P) command and are commonly known as on-the-fly commands (or, more officially, network-side parameters). On-the-fly commands provide a way for the network host to immediately change communications mode of the serial port without rebooting the DS. There are also network-side instructions (Set I/O Pin Status (Sx) and Get I/O Pin Status (Gx)) that are used to set and sense the state of RTS, CTS, DTR, DSR, and also additional P0 and P1 lines* of the DS.
Serial port of the DS has the following capabilities:
* Whether or not these lines are physically implemented depends on the DS model.
** There is not way to set the number of stop bits directly but the second stop-bit can be emulated by setting current Parity (PR) to 3 (mark).
*** HI and LOW states are described with respect to the serial ports of DS100R, DS100B, DS203. For EM100, EM120, EM200, EM203(A) the signaling is exactly opposite.