IRQ Conflict Using MicroGate SDLC Adapter

• Microsoft SNA Server for Windows NT, versions 2.0, 2.1, 2.11, and 3.0

SYMPTOMS

The MicroGate SDLC Link Service may report an IRQ conflict if the MicroGate MG96 or MG144 SDLC adapter is installed in a SNA Server. When you select Adapter Details during the MicroGate link service installation, you will see information similar to the following if this problem occurs:

   I/O Port Address:   0x380
   Interrupt(IRQ):     conflict?
   DMA Channel:        1

   Event ID: 7001
   Source: Service Control Manager
   Description: The SnaMG1 service depends on the IBMSYNC service which
   failed to start because of the following error: A device attached to
   the system is not functioning.

   Event ID: 7000
   Source: Service Control Manager
   Description: The IBMSYNC service failed to start due to the following
   error:
   A device attached to the system is not functioning.

CAUSE

The MicroGate MG96 and MG144 SDLC adapters include a built-in V.32 modem. These adapters are hardwired to use IRQs 3 and 4. Microsoft Windows NT detects IRQ3 as being used by the UART on these adapters during its startup sequence.

WORKAROUND

Change the dip switches on the MicroGate SDLC adapter to have the UART use COM3, instead of COM2, which is the default. The changes must be made via dip switches on the adapter because they are not software configurable. The diagnostics software will allow you to make configuration changes and test the changes. However, the changes are written to a configuration file and do not change the adapter settings.

The default dip switch settings on the adapter are:

S1: 1-8: 01111001 (0=off, 1=on) S2: 1-4: 1111 (all flipped up to ON position)

Change the dip switches to:

S1: 1-8:  10011001               S2: 1-4: 0111

UART = COM3, Base Address = x'03e8', IRQ = 5