ZyXEL Communications U-336E, User Manual

Page: 35 / 137

Basic Modem Operation 23
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, on your PC, be sure to enable the disk cache by
including SMARTDRV execution in your AUTOEXEC batch file.
Default Modem Settings for PC
’
s
The U-336E factory settings are configured for operation with PC
type computers and communication software. In most cases, no
additional settings will be required. The following are some of the
default settings that are used for operation with PC computers and
software:
AT Command Description
E1 Echoes command characters.
&C1 Carrier detect follows remote carrier.
&D2 Modem disconnects on DTR on-to-off
transition.
&K4 Use both V.42 and MNP 4 error correction, and
use both V.42bis and MNP 5 data compression.
&N0 Modem negotiates highest possible connection
speed.