Helpful Hints For Pc Computers - ZyXEL Communications U-336S User Manual

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Helpful Hints for PC Computers

Most PCs are equipped with more than one serial port. Standard
cables are readily available from many suppliers. Usually, serial ports
are manufactured in two forms, either with a 25-pin male jack or a 9-
pin male jack. For high speed serial connections at 230.4Kbps or
460.8Kbps, use a low-capacitance cable. Also, keep the cable as short
as possible.
The serial port is driven by interrupts. Every interrupt needs a certain
amount of overhead processing time. Too many interrupts reduce the
computer's efficiency. The UART 16450 is very commonly used in
serial port devices. For every character (byte) received, it generates an
interrupt. If your hardware allows it and if your software supports it,
replace the 16450 UART with a 16550 model. This newer chip has an
internal buffer and generates an interrupt for up to every 16 characters
(several trigger levels are available). With this UART installed, you may
drive your serial port at 57600 bps and above.
While data is written from the transfer-buffer to your hard-disk,
characters may be lost at the serial port. This is due to the fact that
disk-access interrupts have a higher priority than serial port interrupts. If
you are running at a high serial speed, e.g. 230.4Kbps or 460.8Kbps,
22 Basic Modem Operation
Views the settings in profile (n-1); n=0 to 5; n=0 views
current settings.
Stores the current settings in user profile 'n'; n=0 to 3.
Resets the current settings with the settings in profile 'n',
n=0 to 4.
Factory default profile.