Comtrol RocketPort Windows 98 - Manual (Page 36)

36 Troubleshooting
Windows 95/98
The Windows 3.1 special RocketPort library calls are not supported in
Windows 95/98 (this was supplied for Windows 3.1 only as a means of
opening ports above COM10.)
In Windows 95/98, the current solution is to rewrite the program as a
32-bit program and then use the special sequence \\.\COM11 in the
CreateFile() call.
DCB Device Control Block Parameters
• XonLim, XoffLim - The RocketPort or RocketModem series does not
handle flow control like traditional PC COM ports. Keep in mind
the adapters have large hardware input/output buffers, and any
control strategy based on buffer levels brings the following
question: should the trip point be in reference to the hardware
buffer, or the driver software buffer, or both? And if the hardware
performs the flow control, you cannot consider the software buffer
in the equation. You also need to balance this with efficiency.
RTS/CTS flow control is handled by the RocketPort or
RocketModem card on a hardware level. The RTS trip points are
hardwired to about 7/8 full and empty in relation to the hardware
input buffer of 1,024 bytes.
DTR/DSR flow control is handled at the software driver level. The
DTR trip point is hardwired at the level at which the software input
buffer becomes full (the hardware input buffer of 1,024 bytes still
remains). The low level is XonLim, and is in relation to the drivers
software buffer.
• fOutX - if set, this cause data transmission to halt upon reception
of a XOFF char and resume when a XON char is received. The
XON/XOFF characters are specified by XoffChar and XonChar
parameters and may be changed by the application. The trip points
are hardwired to 7/8 full and empty in relation to the hardware
input buffer of 1,024 bytes.
• fInX - if set, when the receive buffer is near full, an XOFF char will
be sent out to stop the incoming flow of data. When the receive
buffer empties, the XON character is sent to resume incoming data.
The fInX trip point is hardwired at the level at which the software
buffer becomes full (same as DTR above).
• fBinary - Leave this bit set on! ASCII mode (this value at zero)
enables the EOF char to be detected. After the EOF char has been
detected, no more data is allowed to be read, and an overflow error
is displayed if more data is received. While Non-Binary mode is
supported, it should not be used.