usb-serial controller in 5.4?

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i have a USB-Serial Controller by Prolific Technology, Inc.

I tested to see if the device works on FreeBSD on FreeBSD6 machine.
the serial controller works when i load ucom and uplcom modules.
a ucom0 device is generated  along with tty and cua devices.

when i connect to a FreeBSD 5.4 machine with ucom and uplcom modules loaded.
an ucom0 device is generated but the tty and cua devices are not present.
are those not generated automatically in 5.4?  do i need to issue a command
to get the devices working?

TIA,
Tomoki