Contec COM-2DL-PCI, Руководство пользователя, Страница: 49 / 62

4. Functions
42
COM-2PD(PCI)H, COM-4PD(PCI)H
Automatic RTS Control Functions
This function applies to half duplex mode communications.
As half duplex means that the same line is used for sending and receiving, the RTS and CTS signals are
used to switch between sending and receiving. Normally, RTS is set by writing to the corresponding
register bit, but on this board it is controlled by hardware. This reduces the load on the CPU.
If you wish to use this function with the "Standard COM Driver Software COM Setup Disk" from the
CD-ROM, it can be specified by the user application.
Visual C++
Use the SetCommState() Win32 communications API routine to set [RTS_CONTROL_TOGGLE
(0x03)] in the fRtsControl member of the DCB structure.
CAUTION
In Visual Basic, half duplex communication cannot be used via the communication control
(MSComm) as MSComm does not support setting this function.
Other Functions
Channel Isolation/Bus Isolation
The communication lines for each channel are electrically isolated from each other and from the PC.
As isolation is provided between channels as well as isolation of the bus, this prevents electrical
interference between channels as well as between the PC and external circuits.
This means you can safely use the boards in environments where noise is likely to be generated on the
communication lines and where you are concerned about this causing incorrect operation or damage to
the PC.
Surge Protection
As surge protection is provided on all RS-422A/485 control lines, you can safely use the boards in
environments where you are concerned about surges causing incorrect operation or damage to the PC.