Vision Systems VScom 200E PCIex Manual de usuario descargar pdf (Pagina 38)

4 Windows Driver

DTR on Compare the slider of RTS on.

DTR oﬀ Compare the slider of RTS oﬀ.

DSR enable Enables transmission control via the DSR input.

RS 485 operation RS 485 very often uses a shared medium (one pair of wires) to send and receive

data. This requires the ability to disable the transmission unit. It must be oﬀ to receive data, and

must be switched on when transmitting. After transmit is ﬁnished it must be oﬀ again as soon

as possible.

Very often this switching is controlled via signals like RTS or DTR. But in many

environments it is diﬃcult for an application to do this in a reasonable time. Now this option can

help.

Figure 23: Auto-DTR Modes

The UART controls the DTR by itself. As long as data is in the transmission FIFO the DTR

signal is held High (or Low). When the transmission FIFO is empty the DTR changes. An

external converter may monitor this signal to act as needed.

RS 485 usage can be compared to communication over handheld transceiver, many people are

familiar with this. To talk one has to press a button. If two or more persons talk at the same time,

no one can hear clearly. For listening the button has to be released. Now the DTR operates like an

“automatic” button, which presses itself as soon as one starts to talk. And it releases afterwards

while the user is silent.

This feature is very useful for older applications. Often there are applications written for a half-

duplex protocol

over RS 232. Now this may have to operate over a longer distance. So RS 485 is

chosen to transmit the data. But the application does not know about this, and does not control

the RTS or DTR signal. The driver can do this invisible to the application.

4.3 Windows NT 4.0

Windows NT 4.0 is diﬀerent from Windows 2000 and up, and also the no longer supported

strand

of 9x systems (Windows 95 up to ME). These other are all Plug & Play systems, meaning they

will detect

added hardware themselves. Users are asked to provide the required driver ﬁles. In

Windows NT drivers are installed, and fail to load if the hardware is not available.

The VScom drivers for Windows NT implement the Plug & Play functions in a limited sense. There

is a supervisor utility, restricted to detect VScom PCI cards.

Think of it as talking by Walkie-Talkie

XMODEM and YMODEM are good examples

By Microsoft that is, they ceased support for all versions up to Windows 2000

You may even conﬁgure the hardware via Windows

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Vision Systems VScom 200E PCIex Manual de usuario Pagina 38