Installation of COM ports in Windows NT

This document details the installation of COM: ports under Windows NT. Installation notes are included for Non-Intelligent Multi-port and Normal serial interfaces. Non-Intelligent Multi-port serial interfaces are special COM: cards that have an Interrupt Status Register that allows the Device Driver to better service the ports that reside on the card.

WARNING: Be very careful when following the procedure for adding ports. If an error is made, you may need to use the emergency repair disk to recover.

To configure multi-port serial adapters for Windows NT.

1. Determine the best IRQ and port address values for your adapter to use in your computer.

2. Install the adapter according to the manufacturer's instructions.

3. Using Registry Editor, open the key HKEY_LOCAL_MACHINE\SYSTEM\Currentcontrolset\Services\Serial\Parameters (For more information on how to do this, see the on-line help for Registry Editor.)

4. From the appropriate table below, add the Serial* Keys under Parameters and add the corresponding values for each Serial* key. The actual values for your computer may be different. Also, if you have only one serial port on your computer, you may start with Serial1 and Com2:. If no serial ports are built into your computer, you may start with Serial0 and Com1:.

5. If there are no serial ports built into your computer, the following values need to be added under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Serial:
   

Add Value Names         Data Type       Data

ErrorControl            REG_DWORD       1

Group                   REG_SZ          Extended base

Start                   REG_DWORD       2

Type                    REG_DWORD       1

Exit from Regedt32, and enter the following 2 commands to activate the changes:

NET STOP SERIAL
NET START SERIAL

The serial ports should now work. Restarting Windows NT will also activate the changes.

Note that COM1: through COM9: can be directly referenced just like a filename from programs and from the command line. However, COM10: and above must be referenced with the following syntax:

\\.\com10

The command line MODE command does not recognize ports above COM9:.

Sample Configuration Key Values
The sample below assumes that there are two serial ports already available that will be listed as "Serial0" and "Serial1" in the Registry and assigned to COM1: and COM2: respectively. The additional ports will start at COM3:. For more than four port adapters, simply continue the pattern for as many ports as needed.

Example : Quadport 4-port adapter at IRQ10, starting port address 500, starting at COM3:.

You must program the Interrupt Pending Register for the Quadport at 0x0140 or another free range.

The IRQ Pending register will occupy 8 contiguous locations (ie. 0x0140..0x0147)

Serial0 = COM1 and Serial1 = COM2

---

Add Key              Add Value Names      Data Type       Data
(no class)

Serial2              PortAddress          REG_DWORD       0x500
                     Interrupt            REG_DWORD       0x0a
                     DosDevices           REG_SZ          COM3
                     PortIndex            REG_DWORD       1
                     InterruptStatus      REG_DWORD       0x140

Serial3              PortAddress          REG_DWORD       0x508
                     Interupt             REG_DWORD       0x0a
                     DosDevices           REG_SZ          COM4
                     PortIndex            REG_DWORD       2
                     InterruptStatus      REG_DWORD       0x140

Serial4              PortAddress          REG_DWORD       0x510
                     Interrupt            REG_DWORD       0x0a
                     DosDevices           REG_SZ          COM5
                     PortIndex            REG_DWORD       3
                     InterruptStatus      REG_DWORD       0x140

Serial5              PortAddress          REG_DWORD       0x518
                     Interupt             REG_DWORD       0x0a
                     DosDevices           REG_SZ          COM6
                     PortIndex            REG_DWORD       4
                     InterruptStatus      REG_DWORD       0x140


NOTE : You must activate the Quadport IRQ Pending register and apply that 
value in the above structure for the IRQ sharing feature to function.


This feature is available on any of the Quadport products using the latest 
control software.


Also ensure that the IRQ you are selecting is truly conflict free and not
used by another ISA / PCI bus product.

Currently Windows NT supports up to 256 COM: ports although the command line MODE does not support over COM9:.