WavePhore Networks IDR V1000, Руководство пользователя

Страница: 45 / 63

Functional Overview
5– 12 MS-4900, Rev. A
Buffering and
Flow Control Buffering and flow control are important concepts related to moving the data
through the output ports.
The buffer is the area of RAM in the IDR V1000 allocated to temporarily store
processed data when the external computer is unready or unable to accept it. As
soon as the external computer can accept incoming data, the buffers empty as the
data is moved out of the receiver. The memory utilization fields in the IDR V1000
screens describe the current percentage of buffer space being used to temporarily
store data. Memory utilization of 100 percent means the buffer space is overrun;
data is being lost.
Flow control provides a means for the external computer to regulate the data coming
out of the IDR V1000. The following options are available to implement flow
control:
•
RTS (request to send); a hardware-implemented method
•
XON/XOFF (transmit on/transmit off); a software-implemented method
•
RR/RNR (receiver ready/receiver not ready; a WavePhore proprietary software
method)
•
“Both” (an IDR V1000 setup option meaning that both hardware and software
methods are selected)
Another option is to select “none”: to not implement any method of flow control.
Whatever option is selected, both the IDR V1000 and the communications software
running in the external computer must match each other.
If the output device cannot handle the data coming into it from the IDR V1000, it
signals the IDR V1000 to suspend the data flow, using one of four methods. The
IDR V1000 buffers the data until it receives another signal to continue data flow.
Often times, display problems on end users’ computers are caused by flow control
issues. Either rebooting the computer, or reconfiguring it to handle fewer processing
tasks may clear the display problem.
NOTE: Neither RR/RNR or XON/XOFF operate at baud rates of 57600 or
115200.
Serial Output
Ports The output from the receiver typically consists of charts, text, or graphics, and is
intended for display on a personal computer (either standalone or part of a network.)
The IDR V1000 supports a variety of output methods, depending on the model:
•
The basic model supplies one asynchronous serial output port, Serial 1
•
The 4-port daughtercard (Figure 5-5) provides four additional serial ports
•
The Ethernet daughtercard (Figure 5-6) provides a synchronous (high-speed)
output port, an asynchronous output port, and a 10BaseT output to a local area
network.
The settings within the IDR V1000 can be modified to suspend output to a given
port or to isolate a single port for test transmissions only.