Configuring MicroGate T1 SDLC Link Service

The MicroGate T1 SDLC Link Service allows SNA Server to communicate with host, peer, or downstream computers through full or half duplex synchronous serial communications. Supported equipment includes synchronous modems, CSU/DSUs, and ISDN Terminal Adapters.

To configure a MicroGate SDLC Link Service:

Link Service Title

Select the edit control marked Service Title and type a title for the link service (maximum of 40 characters) that will be used to identify the link service. This title must be unique.

Adapter Selection

When installng a new MicroGate SDLC Link Service a new adapter name is created (MGSYNC_1, MGSYNC_2, etc.). This name is used to identify which hardware adapter will be used for this link service. Click on the Settings button next to the adapter selection control to set the hardware settings used by the selected adapter. These settings must match the hardware configuration of the installed adapter.

If the new link service needs to use an existing adapter definition (created when previously installing an instance of this link service type) then select the adapter from the Adapter drop down list.

Line Type

The Line Type determines how and when the link is activated. This setting will depend on the type of communications equipment used. Select the line type by clicking on the appropriate radio button.

Leased

Switched:Server Stored Number

Switched:Modem Stored Number

Switched:Manual Dial

Constant RTS

This setting controls the behavior of the Request To Send signal from the serial adapter to the communications equipment. In order to transmit data  both RTS from the adapter and CTS (Clear To Send) from the communications equipment must be active. If the Constant RTS check box is selected then the adapter will set RTS constantly active. Otherwise RTS will be set active when data needs to be transmitted and the adapter will wait for CTS to go active before transmitting the data. RTS will then be set inactive after the transmission is complete. If possible select Constant RTS for improved performance. Do NOT select Constant RTS for multidrop SDLC configurations.

Dialer Settings

If the Line Type was selected to use the SNA Server Stored Number then the Dialer Settings must be configured. This is done by clicking on the Dialer Settings Button. For other line types the Dialer Settings are ignored.

Internal Clocking

The MicroGate T1 Adapter has the ability to generate a data clock on the AUXCLK pin(s) of the serial interface. The exact pins depend on the selected serial interface (RS-232/V.35/RS-422). See the users manual for the AUXCLK pins for the selected serial interface. This feature is useful for connecting two serial adapters with a modem eliminator. The data rate is in bits per second (bps).


 MicroGate T1 Adapter Settings

This dialog box is used to select the MicroGate T1 Adapter settings. These settings determine which computer resources are used by the adapter and must match the configuration of the installed adapter. Any resources used by this adapter cannot be shared with other adapters so care must be taken during installation to avoid a resource conflict.

These settings include three items:

Input/Output Base Address

The computer communicates with the adapter using a range of hardware ports or registers. This setting determines where these registers are located. The MicroGate T1 adapter uses 16 bytes of I/O address space starting at the base address. If a base address of 300 (hexaal) is selected then the adapter will use the address range of 300 to 30F. Other adapters cannot use I/O addresses in this range.

Interrupt Level

This setting determines which interrupt level will be used by the adapter to request service from the computer.

DMA Level

This setting determines which DMA channel will be used by the adapter to transfer data directly to and from the computers memory.

Max BTU Size

This setting determines the largest Basic Transmission Unit (BTU) size that the driver can support. This does not set the actual BTU size (this is done in the SNA Administrator link service entry) but does place a maximum limit on the BTU size. A larger BTU size can improve data throughput but consumes more memory for buffers. This value should be set to the smallest value that allows the BTU size you need in order to conserve memory. For example: if the BTU size needs to be 6000 bytes then select the 8188 maximum limit. The default value is 8188. If the maximum size is used, it may be necessary to adjust the amount of Non Paged Pool memory used by Windows NT.

When all adapter settings have been selected then click on the OK button.

Clicking on the Cancel button discards any selections.


 Dialer Settings

This dialog box is used to select the MicroGate T1 Adapter dialer settings. These settings control how the adapter sets up and controls a call using asynchronous AT commands. This information is used only if the link service Line Type has been set to Switched:Server Stored Number.

COM Port

This setting specifies the COM port used for sending the AT commands. This is the COM port on the MicroGate T1 Adapter. The COM port must be setup by selecting the Ports icon from the Control Panel. For dialer to operate correctly then Adapter multiplexer mode must be configured for Auto-Switch mode. (see the adapter users guide for more details).

Baud Rate

This setting determines at what speed the COM port communicates with the communications equipment.

Incoming String

This string is the AT command that is sent to the communications equipment to enable it to accept incoming calls.

Outgoing String

This string is the AT command that is sent to the communications equipment to start an outgoing call.

Default Strings

The default Incoming and Outgoing strings should work with most modems, however some modems may require these settings to be customized. Refer to the users guide for your communications equipment for the correct AT commands.

The components of the default Incoming and Outgoing strings are:

&F	Set factory default settings.

&C1	Set switched Carrier Detect (CD) signal from modem.

&S1	Set switched Data Set Ready (DSR) signal from modem.

&D3	Reset modem when DTR signal from adapter goes inactive.

&Q1	Set synchronous communications mode when connected. For some

modems this is &M1.

Q1	Turn off modem result codes.

S0=0	Turn off auto-answer mode. (Outgoing String)

S1=1	Turn on auto-answer mode. (Incoming String)

DT	Dial outgoing number (prefix to actual phone number)


Leased Line Type

This option is used for a dedicated telecommunications line. The line can be a point to point leased line or a multidrop leased line.


Switched:Server Stored Number

This option is used for communications equipment that can accept AT style asynchronous commands for call setup and control. SNA Server is configured with the outgoing call number that is used to automatically setup a call when the link service is activated.


Switched:Modem Stored Number

This option is used with communications equipment that can store an outgoing number and setup a call using that number when the DTR (Data Terminal Ready) signal from the serial adapter is activated.


Switched:Manual Dial

This option is used when the phone number must be dialed manually with a handset. SNA Server will prompt the user when it is time to dial the number.


MicroGate T1 Adapter Memory Usage

The device driver for the MicroGate T1 Adapter requires memory buffers to hold incoming and outgoing frames of data. The buffer size increases with the Max BTU Size. The default Max BTU size is 8188 bytes.

The device driver buffers use a special kind of memory called Non Paged Pool. The amount of available Non Paged Pool is determined at boot time and is a small percentage of the installed physical memory. More Non Paged Pool will be available on machines with more physical memory. There may not be enough Non Paged Pool available for the device driver if the Max BTU Size setting is set to a large value (or multiple adapters are installed with large Max BTU sizes).

If the device driver cannot get enough memory for the buffers then the device will not be available for use and an entry will be made in the system event log indicating the problem. In this case the amount of Non Paged Pool must be increased or the Max BTU Size must be decreased. The amount of available Non Paged Pool can be increased by adding more physical memory or by modifying a registry entry to allocate a larger portion of the current amount of physical memory to Non Paged Pool.

Increasing Non Paged Pool Through the Registry

NOTE: The registry editor should only be used by persons with a thorough knowledge of the Windows NT registry.

There is a registry value which determines the amount of physical memory allocated for Non Paged Pool. Be careful when modifying this value: an incorrect value can prevent Windows NT from booting. The value is located in the following registry path:

HKEY_LOCAL_MACHINE

  \SYSTEM

    \CurrentControlSet

      \Control

        \Session Manager

          \Memory Management

            \NonPagedPoolSize

The default NonPagedPoolSize value is 0. This allows Windows NT to determine the amount of Non Paged Pool based on the amount of installed physical memory. To increase the amount of Non Paged Pool you must set this value to a new fixed value that is based on the current value.

To determine the current Non Paged Pool size run the performance monitor program located in the Administrative Tools program group. Add a counter to the chart by selecting the Add To Chart menu item from the Edit menu. Select the Non Paged Pool Bytes counter for the Memory object.

Take the current value in bytes and add 25%. This will be the new registry entry value.