IRQ on PCMCIA Modem
From: Guenter Resch (spambox_at_telering.at)
Date: 06 Nov 2003 09:21:30 GMT
I'm trying to set up a PCMCIA modem ("Mercury 56k Fax Modem Card", FCC
ID 5HRTAI-31904-M5-E) to work on a Linux notebook with a customised
kernel 2.4.21. In principle, the Modem does work as /dev/ttyS1, but
it's extremely slow.auf einem System mit einem angepassten
Based on what I read in the PCMCIA Howto, the problem is most likely an
| If the modem seems to work only very, very slowly, this is an almost
| certain indicator of an interrupt conflict.
However, at the moment, the modem seems not to use and interrupt but is
"working" in polled mode (IRQ 0):
[root@eclipse pcmcia] setserial /dev/ttyS1
/dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 0
This is most likely the main reason of my problem. From the PCMCIA-Howto:
| ... try using setserial to change the irq to 0, and see if the modem
| works. This causes the serial driver to use a slower polled mode
| instead of using interrupts.
I think I should also mention the output of cardctl, where no IRQ is
shown for the modem in socket 1:
[root@eclipse pcmcia] cardctl config
Vcc 3.3V Vpp1 3.3V Vpp2 3.3V
interface type is "cardbus"
irq 10 [exclusive] [level]
Vcc 5.0V Vpp1 0.0V Vpp2 0.0V
interface type is "memory and I/O"
speaker output is enabled
config base 0x0100
option 0x61 status 0x08 ext 0x00
io 0x02f8-0x02ff [8bit]
So I have two questions:
- How can I find a free IRQ? Is this just by looking for missing entries
in /proc/interrupts? What irritated me a bit was that /dev/ttyS0 is on
IRQ 4 (setserial) but not shown upon cat /proc/interrupts.
- On a RedHat system, how do I assign the free IRQ I found to the modem
correctly? Trying to change SERIAL_OPTS in /etc/pcmcia/serial.opts was
not very successful (I could get the modem to use anIRQ but it did not
Thanks in advance,