EtherPADs are available in either RS232 or RS422/485 Hardware Configuration RS485/422 EtherPADs can be identified by a Phoenix 8-pin inline
terminal connector.
The following operations are supported:
Point-to-Point/4 -wire Full-Duplex.
Point-to-Point/2-wire Half-Duplex
Multidrop/4 -wire Full-Duplex.
Multidrop/2-wire Half-Duplex
Setting Up the RS485/422 Interface
Web Browser
Click on Device Interfaces.
To configure the Device Interface, click on Change.
Device Interface configured for RS232/RS422 (full-duplex or direct) operation.
Device Interface configured for RS485 (half-duplex) operation.
Telnet or Serial Configuration
Select '3. Device Interfaces'
Device Interface configured for RS232/RS422 (full-duplex or direct) operation.
Device Interface configured for RS485 (half-duplex) operation.
Device Interface Parameters
- Interface Number: Displays the application port number. This value is read only.
- Data Bits: Values between 5 and 8 can be selected. The default is 8.
- Stop Bits: Values of 1 or 2 can be selected. The default is 1.
- Parity: Cycles the parity between None, Even, Odd, Mark or Space. The default is None.
- Baud Rate: Serial data speeds of 300, 600, 1200, 2400, 4800, 9600, 14400, 19200, 28800, 38400, 57600 and 115200 Bps can be selected.
The default is 19200.
- Flow Control: Select between Hardware (RTS/CTS), Software (XON/XOFF) and None.
Note: Flow control is a mechanism for various communication devices to deal with one device sending data faster than the other can receive it.
Flow control works by allowing one device to ask the other to pause while it catches up. There are three common types of flow control used: hardware,
software, and none. Flow control is not necessary when the transmission speed is very slow, such as 300 baud or 300 bits per second (bps), and the
devices at each end are reasonably fast.
- Connection Type: Direct (Full-Duplex RS232 or RS422); Half-Duplex (Half-Duplex connections for use with RS485).
- Protocol: The serial protocol used to communicate with the device. Supported protocols are:
None - No protocol configured. This allows the interface to be used for PPP if required.
Raw - Data is transmitted transparently between the EtherPAD and the device.
TC500 - The Burroughs TC500 protocol, as currently used with ATM's.
Note: If you wish to run PPP over this Serial Interface, the Protocol field must be set to 'None'.
- Maximum Message Length: The maximum 'message' length used by the EtherPAD. Once the EtherPAD receives the specified number of bytes from
the serial device, the received data will be forwarded to the configured Device Applications. Valid values are 0 to 1024, with the default being
1024 bytes. A value of 0 indicates that the maximum message length (1024) be used.
- Message Timeout: The maximum period (in milliseconds) the EtherPAD will wait for a 'message' to be received from the serial device before
forwarding the received data to the Device Applications. Valid values are 0 to 60000, with the default being 4000 (4 seconds). A value of 0 specifies
the default of 6 seconds.
- Message Terminator: If enabled, the single character (decimal ASCII code 0 to 255) that is used to indicate the end of a 'message' received
on the serial device. The default is 13. For example, setting this to 13 (carriage return) causes received serial data to be forwarded to the Device
Applications immediately after receiving a Carriage Return character
Impedance Matching and Termination Resistors
When an electrical signal travels through two different resistance junctions in a transmission line, the mismatch will sometimes cause signal reflections.
This reflection causes signal distortion that contributes to communication errors. The solution to this problem is to establish the same impedance at the
line ends as in the line itself by terminating the line ends with resistors. Normally it will be sufficient when the value of the termination resistor
equals the characteristic impedance of the transmission lines. The resistors should then be added near the receiving side.
Isolation Protection
The RS485 EtherPADs provide isolation protection, which protects against high voltages up to 2000 V.
Hardware Settings
