Installing an SDLC Link Service

An SDLC Link Service enables SNA Server to communicate with host, peer, or downstream computers through full-duplex or half-duplex synchronous modems, over switched or leased telecommunication lines.

SDLC is IBM's implementation of a bot-oriented serial protocol with a standardized frame reader and block check sequence. SDLC applies to synchronous transmissions; it organizes information in rigidly structured units called frames.

To Install a new SDLC Link Service:

1  From the main Link Service Installation Dialog Box, select Digi SDLC Link Service (if the service is already available) or click other to install Digi new service.

2  Select Digi SDLC Link Service and click install.

3  Digi SDLC Link Support - Installation Dialog appears.

4  The name of this service (SnaSdlc1) appears in the Dialog Box. This name will be a sub-key under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services. The number (that is appended to the Service Name) is the instance number (i.e., Link Service #1 - SnaSdlc1, Link Service #2 - SnaSdlc2, etc.).

5  The title for this service may be changed. Just delete the default and type the new title. You can use as many as 40 characters for this title.

6  Since every Link Service requires a Device Object be associated with it, the New Connection Id refers to the Device Object Instance.  Every Device Object Instance controls a Hardware entity defined in the Details Dialog Box. Clicking the Details Button presents the Digi SDLC Physical Connection Setup Dialog Box.

7  In the Board Base I/O Addr Combo Box, select the board  base you will be using. Currently, all possible base I/O Addresses are provided as options. The user is responsible for making sure that the actual board base I/O Address matches the one selected in the Combo Box.

8  Under Line Type, select the appropriate option:

  Leased
  Switched: Server-Stored Number*
  Switched:  Modem-Stored Number
  Switched:  Manual Dial

*Select the Switched: server Stored Number option only if the SDLC adapter to which the modem is attached has a built-in-serial (COM) port. For more information, see:

Requirements for Using Server-Stored Numbers
Routines Used with Server_Stored Numbers

9  If you like the line to use constant RTS, select the Constant RTS option. For more information see:  Notes about Constant RTS.

IMPORTANT:	Do not select Constant RTS option when configuring this link service for use by multidrop connection. Multidrop connections allow multiple SDLC connections to connect to the same physical wire. Usually SDLC is a point-to-point connection protocol.

10  Choose Continue. This setup copies the required files, and the Link Service Configuration dialog box appears, listing the new entry for this Link Service.


Leased

Choose this option for a dedicated telecommunications line. The line can be a point-to-point leased line or a multidrop leased line.


Switched: Server-Stored Number

Choose this option if the modem can accept a phone number from SNA Server, that is, if the SDLC adapter to which the modem is attached has a built-in-serial (COM) port.


Switched Modem-Stored Number

Choose this option for a modem that stores a phone number. Make sure that the modem is configured to dial the number when the Data Terminal Ready (DTR) is raised, in conformance with the IEEE RD 232 Modem Specification for line 108.1.


Switched: Manual Dial

Choose this option if you will dial the phone number. SNA Server will prompt you when it is time to dial the number.


Requirements for Using Server_Stored Numbers

In order to accept a phone number from SNA Server, your modem must be set up so that it will:

  Accept dial commands in ASCII (eight data bits, no parity bit, one stop bit).

  Set Clear to Send (CTS) and Data Set Ready (DSR) to on when ready to accept dial commands.

  Set DSR to off after accepting a dial command.

  Set DSR to on again when (and only when) the dialed connection is made.

  Change to synchronous mode after the dial up has completed.

  Change back to dial-command mode if Data Terminal Ready (DTR) is dropped and raised again.


Routines Used with Server-Stored Numbers

When SNA Server is sending a phone number to a modem, it ignores modem responses and holds the modem interface signals Select Standby and DTR to off.

The dialing attempt initiated by SNA Server is assumed to have failed if one of the following occurs:

  DSR stays on after the dial string has been sent.

  The connection time-out expires before DSR comes on to indicate that the call is connected.

When SNA Server creates a dial string to send to a modem, it uses the outgoing command string supplied in setup as a base, and then appends the Dial Data (Phone Number) configured in SNA Server Admin, followed by a carriage-return and line-feed sequence.


Switched SDLC Line

A standard dial-up telephone line used for asynchronous data link control (SDLC) connections.


Leased SDLC Line

A telecommunications line committed solely to use by the synchronous data link control (SDLC) connections. The line may be used for point-to-point connections or multidrop connections.


Board Base I/O Addr

Before Installing the SYNC/570 or SYNC/570i in any system, set the multi-segment switch on the board. The setting of the switch selects the starting address of the block of I/O locations which the SYNC/570 or SYNC/570i uses.

The board is shipped with a default setting of 300H.

The Combo boxes provide with all the commonly used options.

The Dialog Box Item specifies the board that was used when installation took place.


Constant RTS

Constant Request To Send is an option that causes the SDLC adapter to be in constant readiness to send data. This option is required if a line is to be used for full duplex. It cannot be used with Multidrop. Multidrop connections allow multiple SDLC connections to connect to the same physical wire. Usually SDLC is a point-to-point connection protocol.

If an SDLC adapter does not use Constant RTS, before the adapter can send data, it must raise RTS and then wait for the Remote end to raise CTS (Clear To Send). In contrast, an adapter that uses the constant RTS holds RTS high so CTS is always high, and the wait is eliminated.


Notes About Constant RTS

For higher throughput, choose Constant RTS whenever you can. It is generally used on leased lines and is often available on Modems for Switched connection as well.

However, do not select this option when configuring this link service to be used by a Multidrop connection (multidrop connections allow multiple SDLC connections to connect to the same physical wire).


Notes on Complete Installation

By complete installation, it is meant that the Physical Connection Setup - Installation  Dialog Box allows the user to configure all the available parameters (Memory  Base, Interrupt Level, Port Number & Line Speed). This takes place when there are no other  installed link services  using the same Board Base I/O Address.  The Partial installation, on the other hand, disables the Board Settings (Memory Base & Interrupt Level) and allows the user to configure the Port Settings only.


Partial Installation

By partial installation, it is meant that the Physical Connection Setup - Installation  Dialog Box allows the user to configure some of  the available parameters (Port Number & Line Speed). This takes place when there are other  installed link services  using the same Board Base I/O Address.  The Complete installation, on the other hand, enables the Board Settings  and the Port Settings as well.


Notes on Configuration

By configuration, it is meant that the Physical Connection Setup - Configuration  Dialog Box allows the user to re-configure some of  the available parameters (Port Number & Line Speed).


Configuring an SDLC Link Service

This setup dialog gets invoked when the user decides to configure a pre-installed Link Service.  The following is very similar to the Link Service Installation, there are, however, few differences.

An SDLC Link Service enables SNA Server to communicate with host, peer, or downstream computers through full-duplex or half-duplex synchronous modems, over switched or leased telecommunication lines. SDLC is IBM's implementation of a bot-oriented serial protocol with a standardized frame reader and block check sequence. SDLC applies to synchronous transmissions; it organizes information in rigidly structured units called frames.

To Configure a pre-installed SDLC Link Service:

1  From the main Link Service Dialog Box, select Digi SDLC Link Service #n (where n denotes the service instance - the service should be already available). Click "Configure" to configure Digi service.

2  Digi SDLC Link Support - Configuration Dialog appears.

3  The name of this service (SnaSdlc1) appears in the Dialog Box. This name will be a sub-key under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services. The number (that is appended to the Service Name) is the instance number (i.e., Link Service #1 - SnaSdlc1, Link Service #2 - SnaSdlc2, etc.).

4  The title for this service may be changed. Just delete the default and type the new title. You can use as many as 40 characters for this title.

5  Since every Link Service requires a Device Object be associated with it, the Configured Connection Id refers to the Device Object Instance.  Every Device Object Instance controls a Hardware entity defined in the Configure Dialog Box. Clicking the Configure Button presents the Digi SDLC Physical Connection Setup Dialog Box.

6  In the Board Base I/O Addr Combo Box, select the board  base you will be using. Currently, all possible base I/O Addresses are provided as options. The user is responsible for making sure that the actual board base I/O Address matches the one selected in the Combo Box.

7  Under Line Type, select the appropriate option:

  Leased
  Switched: Server-Stored Number*
  Switched:  Modem-Stored Number
  Switched:  Manual Dial
  Switched:  Modem-Stored Number
  Switched:  Manual Dial

*Select the Switched: server Stored Number option only if the SDLC adapter to which the modem is attached has a built-in-serial (COM) port. For more information, see:

Requirements for Using Server-Stored Numbers
Routines Used with Server_Stored Numbers

8  If you like the line to use constant RTS, select the Constant RTS option. For more information see:  Notes about Constant RTS.

IMPORTANT	Do not select Constant RTS option when configuring this link service for use by multidrop connection. Multidrop connections allow multiple SDLC connections to connect to the same physical wire. Usually SDLC is a point-to-point connection protocol.

9  Choose Continue. The setup accepts the new inputs and updates the registry sub-key.


Installing a New Physical Connection (Complete Installation)

Every Link Service requires a Device Object Physical Connection. All the inputs in this Dialog are hardware settings. The settings are divided into two categories: Board Settings & Port Settings.

The Board Settings specify the Base Memory and the Interrupt level, whereas the Port Settings specify the Port Number and the Line Speed.

To Install a new Physical Connection:

1  From the Digi SDLC Link Service Installation main Dialog Box, click the Details Button. The Digi SDLC Physical Connection Setup - Installation Dialog Box appears.

2  The adapter name displays the Digi SYNC/570 and the Board Base Address.

3  The Device Name displays the Physical Connection Instance Name (Device Object) and Number.

4  This is a complete installation Dialog Box because there are no other Link Services installed with the same board base.

5  Under Board Settings, select the appropriate options:

  Base Memory
  Interrupt Level

6   Under  Port Settings, select the appropriate options:

  Port Number
  Line Speed

7  Choose Continue. The setup accepts the input data and returns to the Digi SDLC Link Support Installation Dialog Box.


Base Memory
Board Base Memory or the Memory Address Register

The memory Address Register is located in a byte within I/O space at an offset of 0x0D from the adapter I/O base address. It provides the starting memory address of the adapter. You will be asked to specify a 16KB memory windows location.

You may always specify FFC000H to indicate that the adapter base memory is the last 16KB of the 16MB address space. This choice would always work if (and only if) the main memory does not exceed FFC000H. However if the main memory exceeds 16 MB (1000000H), then you have to choose among the other possible choices listed below:

C0000

C4000

C8000

CC000

D0000

D4000

D8000

DC000


Interrupt Level

The Digi Board interrupts the processor at this interrupt level.

The Digi board supports the following Interrupt level selections:

IRQ3

IRQ5

IRQ7

IRQ10

IRQ11

IRQ12

IRQ15


Port Number

The Digi Board supports multiple ports. The SYNC/570 series supports 2 ports and the SYNC/570i series supports 4 ports.

The Partial installation limits the Port Settings Options to only those ports that have not been already installed. For example, if the user installed a Physical Connection using Port Number 1, the partial installation dialog box limits the Port Number Settings  to: 2, 3 or 4 preventing the user to install a Link Service that uses the same port number as another (and hence rendering both Link Services inoperable).


Line Speed

The synchronous line speed may be configured as one of the following settings:

2400

4800

9600

19200

38400

56000

64000


Installing a New Physical Connection (Partial Installation)

This setup dialog is invoked when the user decides to install a new Physical Connection and the base board that is selected has already been assigned to another Physical Connection. This happens only when more than one Link Service is being installed. This installation dialog box disables the Board Settings and limits the Port settings (these limits are discussed in the following paragraphs).

Every Link Service requires a Device Object Physical Connection. All the inputs in this Dialog are hardware settings. The settings are divided into two categories: Board Settings & Port Settings.

The Board Settings specify the Base Memory and the Interrupt level, whereas the Port Settings specify the Port Number and the Line Speed.

To Install a new Physical Connection:

1  From the Digi SDLC Link Service Installation main Dialog Box, click the Details Button. The Digi SDLC Physical Connection Setup - Installation Dialog Box appears.

2  The adapter name displays the Digi SYNC/570 and the Board Base Address.

3  The Device Name displays the Physical Connection Instance Name (Device Object) and Number.

4  This is a partial installation Dialog Box because there are other Link Services installed with the same board base.

5  Under Board Settings, the settings are provided automatically. You may not change them.

6  Under Port Settings, select the appropriate options:

  Port Number
  Line Speed

7  Choose Continue. The setup accepts the input data and returns to the Digi SDLC Link Support Installation Dialog Box.


Configuring a Physical Connection

This setup dialog is invoked when the user configures a Physical Connection. This configuration dialog box disables the Board Settings and enables the Port settings.

Every Link Service requires a Device Object Physical Connection. All the inputs in this Dialog are hardware settings. The settings are divided into two categories: Board Settings & Port Settings.

The Board Settings specify the Base Memory and the Interrupt level, whereas the Port Settings specify the Port Number and the Line Speed.

To Configure a Physical Connection:

1  From the Digi SDLC Link Service Configuration Dialog Box, click the Configure Button. The Digi SDLC Physical Connection Setup - Configuration Dialog Box appears.

2  The adapter name displays the Digi SYNC/570 and the Board Base Address.

3  The Device Name displays the Physical Connection Instance Name (Device Object) and Number.

4  This is a Configuration Dialog Box because there are no other Link Services installed with the same board base.

5  Under  Board Settings, the settings are provided automatically. You may not change them.

6  Under  Port Settings, select the appropriate options:

  Port Number
  Line Speed

7  Choose Continue. The setup accepts the input data and returns to the Digi SDLC Link Support Installation Dialog Box.