Linux Kernel Directly Supports SyncLink Adapter Connections.

The SyncLink family of adapters for Linux (USB, PCI, PCI Express, PC/104+) are high-speed serial communications adapters for X86 computers running the Linux operating system, version 2.4 and later. The adapters connect to remote routers or computers using a variety of wide area networking services including DDS, ISDN and T1/E1. SyncLink and its device driver are designed to support both single and multi-processor operation, as well as, 64-bits under x86_64 architecture, while using Linux.

Designed for use with analog, ISDN, and digital CSU/DSU data communications equipment, the adapters support data rates up to 10 Mbps.

Through its serial data interface, which can be configured as V.35, RS-232, or RS-422/485 (RS-530, RS-449, X.21) SyncLink cables directly to data communications equipment such as high-speed synchronous modems and digital service CSU/DSUs, as well as, satellite and RF modems. Multiple port SyncLink adapters support the same connections through independently configured serial data interfaces. Available conversion cables are required for each port for V.35, RS-449, RS-530, and X.21 applications.

SyncLink features plug and play configuration of adapter resources, such as I/O base address and interrupt request level. The number of adapters that can be installed is limited only by the number of available expansion slots.

APPLICATIONS

Application Program Interface.

Linux application programs call the SyncLink device driver using the standard tty device interface, which offers a familiar and documented method for application control.

PPP (with Multilink support) Communications.

The Point-to-Point (PPP) protocol provides network communications between two devices connected by point-to-point media such as a serial connection. Dialup applications usually use asynchronous serial communications running on the standard COM serial ports found in most PCs. High-speed applications typically use synchronous (HDLC) serial communication which is not supported by the standard COM ports.

The SyncLink adapter and device driver provides both asynchronous and high-speed synchronous connections that can be used by the standard Linux PPP software (pppd). The pppd program supports a variety of network protocols including IP, IPX, and Appletalk. Multilink PPP is also supported to combine the bandwidth of multiple serial links into a single logical network connection.

Cisco HDLC.

The SyncLink WAN adapter supports the proprietary Cisco HDLC point-to-point protocol using the syncppp Linux driver.

HDLC Communications.

Applications can call the SyncLink device driver directly to support high-speed synchronous HDLC communications over a serial data connection.

Custom HDLC applications.

The SyncLink device driver provides complete control over serial formats and options. This allows custom applications to use the driver for any variant of HDLC communications such as SNA/SDLC, X.25 and Frame Relay.

SOFTWARE

All SyncLink software includes source code released under the GNU General Public License (GPL). The following Linux software is included:

Device driver: synclink_gt.o synclink_cs.o

The driver uses the standard tty device interface for compatibility with existing applications. Enhancements for synchronous communications and option configuration are provided. Custom HDLC applications communicate directly with the device driver. Other applications may communicate with intermediate software such as the PPP driver which then uses the SyncLink driver.

HDLC Line Discipline: n_hdlc.o

The HDLC line discipline is a loadable module that allows the SyncLink device to be used for custom HDLC applications. This module alters the behavior of the standard read/write system calls to the tty device to enforce a frame oriented (instead of character oriented) interface.

Configuration utility: mgslutil

This command line utility provides a method for shell scripts and users to configure the SyncLink adapter options. Options include switching mode (HDLC or asynchronous), serial encoding (NRZ/NRZI), data clocking, and more.

Sample HDLC application: mgsltest

The sample program demonstrates the use of the SyncLink adapter for custom HDLC applications. HDLC frames are sent and received with statistics output to the display. When combined with an external loopback device, such as a CSU/DSU in loopback mode or the loopback connector provided with the adapter, this program can be used to verify the correct operation of the adapter.