Advantech EKI-1500 Series, User Manual, Page: 48 / 88

EKI-1500 Series User Manual 38
The EKI-1500 Series provides Multi-access function through an Ethernet connection
path, allowing a maximum of five connections to open one serial port simultaneously.
In this mode all connections must use the same serial setting. If one serial setting
within 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-1500 Series will operate in
normal mode. When multiple hosts simultaneously open the serial port, only the first
connected host obtain management control, the remaining connections only have
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-
1500 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-1500 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-1500 Series Series operates
in “Round-Robin mode”. Each serial port supports up to five simultaneous connec-
tions 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-1500
Series processes the data in the order arrived. The EKI-1500 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-1500 Series serial
device server does not receive a response from the serial port after a response time-
out 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 an important parameter for Round Robin mode. The parameter is a
smart method of reducing ineffective waiting periods and streamlining the transmis-
sion process.
If the Frame Break function is disabled, EKI-1500 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-1500 Series assumes the communication is completed and continues with
the next query. This is an efficient way to reduce waiting time and improve perfor-
mance.