Advantech EKI-1528CI, User Manual

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35 EKI-1528-DR Series User Manual
this configuration is configured differently, the data communication will not function
correctly.
Figure 4.2 Configuring Virtual COM Mode
The Host Idle Timeout setting monitors the connection between the host and the
device. If the Host Idle Timeout setting time is reached, the device server will release
the resources allocated to the port mapping. This prevents a stalled host from affect-
ing the connective device.
The Multi-access function has two modes. One is Normal mode and the other is
Round-Robin mode .
4.2.1 Normal mode
By disabling the Response Timeout parameter, the EKI-1528 Series will operate in
normal mode. When multiple hosts simultaneously open the serial port, only the first
connected host has management control; the remaining connections only have a
data communication function. Each serial port supports up to five simultaneous con-
nections, so multiple hosts can transmit/receive data to/from the same serial port
simultaneously. Every host can transmit data to the same serial port, and the EKI-
1528 Series will also transmit data to every hosts. When the multiple hosts transmit
data to the same serial port at the same time, the received data from Ethernet and
the outputs of serial port are mixed. When the EKI-1528 Series receives data from
serial port, the data will also be transmitted to the connected hosts simultaneously.
4.2.2 Round-Robin mode
By enabling the Response Timeout parameter, the EKI-1528 Series operates in
“Round-Robin mode”. Each serial port supports up to five simultaneous connections
allowing hosts to simultaneously transmit/receive data to/from the same serial port.
Every host can simultaneously transmit data to the same serial port, EKI-1528 Series
processes the data in the order arrived. The EKI-1528 Series processes the first
host’s request and replies. The serial device server determines the end of the serial
acknowledgement through a response timeout. When EKI-1528 serial device server
does not receive a response from the serial port after a response timeout query, the
device replies with an acknowledgement and then processes the next host request.
With an increased number of hosts, response time may be lengthy, increasing the
period of the Response Timeout.
Frame Break is therefore an important parameter
for Round Robin mode. The parameter is a smart method of reducing ineffective wait-
ing periods and streamlining the transmission process.
By disabling the Frame Break function, EKI-1528 Series devices will wait for a
“Response Timeout” period, whether or not the device has transmitted data. During
this period, the host commands are queued and processed in the order received.
If Frame Break is enabled, the serial port idle is longer than the Frame Break period.
The EKI-1528 Series assumes the communication is completed and continues with