Installing and Administering PPP

Appendix A 161
Modem Connections
Dial Up Modems
Setting Hardware Flow Control
The output in step 3 of “Adding the Devices” shows that neither device
has hardware flow control set. This is indicated by the zero (0) in the
next to last place of the minor device number in each line. This example
shows how to turn on hardware flow control by creating new devices with
the proper minor mode bits set to one (1).
1. Write down the following information before proceeding to the first
step of setting the hardware flow control:
• the major number (1 in the above example)
• the minor numbers (0x000001 and 0x000002 in the above
example)
2. Rename the devices by issuing the following commands. This saves
your original device configurations under new names. If you ever
need to revert to devices that do not have hardware flow control set,
you can move the original files back into place.
mv /dev/cul0p1 /dev/cul0p1.orig
mv /dev/ttyd0p1 /dev/ttyd0p1.orig
3. Use the mknod(1) command, as shown, to create new devices with
hardware flow control, changing only the hardware flow control bit
from “0” to “1”.
mknod /dev/cul0p1 c 1 0x000011
mknod /dev/ttyd0p1 c 1 0x000012
4. Type the following and check your work by examining the output.
ls -l /dev/cul0p1 /dev/ttyd0p1
crw-rw-rw- 1 root sys 1 0x000011 Jul 8 14:09 cul0p1
crw-rw-rw- 1 root sys 1 0x000012 Jul 8 14:09 ttyd0p1
Notice that the hardware flow control bit is now set to “1”. Make sure
your modem is set up for hardware flow control as well. For closure, set
the permissions and ownership to be the same as they were when the
devices were first created via SAM.
Some modems may refuse to answer the phone if RTS recognition is
enabled and RTS from the HP is low. Even when uugetty is used to
enable incoming calls on the port, these modems will not answer the call
because uugetty does not assert the RTS signal into the modem. The
solution is to turn off RTS recognition on the modem. This is usually