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PCI-COM422/4 Manual
Page 3-2
Manual MPCICOM422-4.E1b
Interrupts
Please note that, in Windows NT, changes must be made to the system registry to support IRQ
sharing. The following is excerpted from "Controlling Multiport Serial I/O Cards" provided by
Microsoft in the MSDN library, documentid:mk:@ivt:nt40res/D15/S55FC.HTM, also available in the
WindowsNT Resource Kit. The text enclosed in brackets ("[ ]") denotes a comment by ACCES.
The Microsoft serial driver can be used to control many dumb multiport serial cards. Dumb indicates
that the control includes no on-board processor. Each port of a multiport card has a separate subkey
under the CurrentControlSet\Services\Serial subkey in the registry. In each of these subkeys, you must
add values for DosDevices, Interrupt, InterruptStatus, PortAddress, and PortIndex because these
are not detected by the Hardware Recognizer. (For descriptions and ranges for these values, see
Regentry.hlp, the Registry help file on the WindowsNT Workstation Resource Kit CD.)
For example, if you have a four-port PCI-COM422/4 card configured to use address 0xFFF0 with an
interrupt of 0xFFF8, the values in the Registry are: [assuming that every port is configured to use the
same IRQ and that the addresses are configured to be consecutive and contiguous]
Serial2 Subkey: Serial4 Subkey:
PortAddress = REG_DWORD 0xFFF0 PortAddress = REG_DWORD 0xFF90
Interrupt = REG_WORD 5 Interrupt = REG_DWORD 5
DosDevices = REG_SZ COM3 DosDevices = REG_SZ COM5
InterruptStatus = REG_DWORD 0xFFF8 InterruptStatus = REG_DWORD 0xFFF8
PortIndex = REG_DWORD 1 PortIndex - REG_DWORD 3
Serial3 Subkey: Serial5 Subkey:
PortAddress = REG_DWORD 0xFFE0 PortAddress = REG_DWORD 0xFF80
Interrupt = REG_DWORD 5 Interrupt = REG_DWORD 5
DosDevices = REG_SZ COM4 Dos Devices = REG_SZ COM6
InterruptStatus = REG_DWORD 0xFFF8 InterruptStatus = REG_DWORD 0xFFF8
PortIndex = REG_DWORD 2 PortIndex = REG_DWORD 4