1.134 Comstream-Modem-Card-SCPC

This page describes the device driver and the device window for the Comstream 5MBit and 512kBit Modem Cards. With this driver you can address up to three modem cards in one CM701 frame as separate devices. To do this, simply configure multiple modems of this type at the same serial port and setup the configuration parameters for each particular modem / modem card as described later in this chapter.

The modem card device driver prepends the modem card's slot number to all commands and individually addresses the card in the modem frame this way. The modem does not support the "primary data rate" macros in this mode, hence the driver is limited to SCPC configurations.

Comstream CM701 device driver overview

The Comstream CM701 satellite modem may be operated in many different configurations. The modular architecture of this device permits to compose a modem from modulator, demodulator and option cards as well as to run up to three modem cards in one device frame.

With the sat-nms software, there is a family of device drivers which cover the most usual configurations for the CM701. Basically there are two groups of drivers: The first one covers applications which make use of the option cards like the framer/buffer card for IDR or the Reed-Solomon codec. This group is limited to single channel (one modulator, one demodulator) usage.

The other group covers multi-channel applications which run up to three modem, modulator oder demodulator cards in one device frame. These drivers are limited to plain SCPC applications, they do not support any option cards. You may put two modem cards and a modulator card in a CM701, these cards will be treated individual devices with the sat-nms software. Below there is a list of the available drivers for the CM701:

Modem cards, modulator cards and demodulator cards may be mixed in one CM701 frame if they are operated with a driver marked as MULTI-CH.

Device window pages

The following table shows which device window pages are available with this individual device type. Tool-bar functions not mentioned here are described at the general description of device windows .

• --- The IF parameters (frequency, level, etc.) and some global modem settings.
• --- The modulator settings, transmit clocking.
• --- The demodulator settings, receive clocking, doppler buffer.
• --- The TX interface settings.
• --- The RX interface settings.
• --- The receive quality.
• --- The faults page.
• --- The device info page.
• --- The maintenance page. The configuration parameters described below are set at this page.

Configuration parameters

At the maintenance page of the device window there are a couple of configuration parameters which must be set to make the software talk to the modem card.

• parameter --- description
• address --- The modem frame RS485 packet address. Valid addresses are 1..31, 31 is the factory default. If you have multiple devices connected to one RS485 bus, each device must have it's unique address.
• slot --- You must set this parameter to the slot number (5..7) where the modem card you want to address is installed.
• faultMask --- The modem's fault mask (both, the STO and the FO mask). Common values are:
  • 4294967295 --- All faults enabled.
  • 1440583691 --- RX faults disabled (TX-ONLY mode)
  • 2863594484 --- TX faults disabled (RX-ONLY mode)

See the Comstream manual for mode details. This parameter applies to all modem cards installed in the device frame.

• faultLogMask --- The modem's fault log mask (FLO), coded in the same way as "faultMask". This parameter applies to all modem cards installed in the device frame.
• txAutoOn --- The carrier state when the modem gets powered on.
• txFaultOff --- Defines if the modems switches off the carrier on some faults conditions.
• vsatMode --- Turns the VSAT mode on/off
• demodLength --- The "DL" parameter. See the Comstream manual for details.
• Serial --- Remember to set the line parameters for the serial interface connected to the modem. While a CM701's factory preset setting is 1200,O,7,1 , the recommended line setting for the use with the sat-nms software is 9600,O,7,1 .

Communication protocol / Interface type

The recommended communication protocol for the CM601/CM701 modems is the Comstream-Packet-Protocol (The driver works with the Comstream-ASCII-Protocol , too, but there are several issues when using the ASCII protocol (unsolicited "ST/FL" reports, multi-line terminal commands). You are free to use either a RS232 or a RS485 interface to access the modem.

Commonly Asked Questions

The CM701 does not seamlessly fit into the M&C software concept at some points. Commonly asked questions arising from these issues are answered below.

• One of the IF frequency fields at the user interface contains no value. Why? --- The CM701 uses a flexible format for IF frequency values. It remembers the number of digits the last command contained and replies to all following requests with this number of digits. This may lead to a wrong reading if the modem is operated with the software the fist time. Once the frequency has been set by the software one time, the CM701 reports the correct frequency value and the software display this.
• What do the "set to xxx but reported yyy" messages in the event log mean? --- The range of some parameters of the CM701 depend on other parameter settings. For instance, the Reed-Solomon scrambling type only can be selected, if the Reed-Solomon codec is present and enabled. If not, the CM701 reverts to the old setting an one of these messages appears in the event log. Another parameter commonly causing such messages is the doppler buffer size. The value always must be a power of two, the CM701 automatically uses the next possible value above if you enter some other numbers.

Variables defined by this device driver