TABLE OF CONTENTS
NOTES on SDM300a
SATELLITE MODEM
Baud Rates of the satellite modem
| 150 | 2400 |
| 300 | 4800 |
| 600 | 9600 |
| 1200 | 19200 |
Important Parameters to Change Before Testing or Final Implementation of the Serial Port Program.
TIME:HH:MM:SS AM/PM
DATE:MM/DD/YY
Time of day and date display/set
function. The current time and date in the modem's memory are displayed
when selected. To change the modem time and/or date, press. Press <-
or -> to position the cursor over the parameter to be changed. Press up
arrow key or down arrow key to change the parameters. Once the parameters
are displayed as desired, press to set the time and date.
REMOTE BAUD RATE
X PARITY
The parity and baud rate settings
of the modem are displayed. To change the modem baud rate and/or parity,
press. Press [<-] or [->] to position the cursor over the parameter
to be changed. Press up arrow key or down arrow key to change the parameter.
Once the parameters are displayed as desired, press to set the baud rate
and parity.
REMOTE ADDRESS
The current modem address is displayed
(1 to 255). To change the remote address, press. Press up arrow key or
down arrow key to make the selection. Press to execute the change.
To communicate with the established
remote communications protocol, configure each modem for one address between
1 and 255. Each modem on a common remote communication link (EIA-485) must
have a distinct address.
Note: Address 0 is reserved as a global address which simultaneouly addresses all devices on a given communications link.
REMOTE TYPE
Select EIA-485 (2 wire), EIA-485
(4 wire), or EIA-232
An EIA-485/EIA-232 comm link remotely
controls and monitors all modem functions. Use the 2- or 4-wire, half-duplex
EIA-485 interface to connect between two or more modems and switches on
a common communication link. Use the EIA-232 interface to communicate with
a single modem.
EIA-232 SPECIFICATIONS
Circuit Supported:
TXD, TXC, RXD, RXC, DSR, DCD, CTS,
LL, RTS, MC
Driver Amplitude (RXD, RXC, ST,
CTS, DM, DSR)
True: 10V, ±5V
False: -10V, ±5V
Receiver Amplitude (TXD, TXC, RTS,
LL, MC)
True: Min +1V
False: Max -1V
Impedance: 5000, ±2000 W
< 2500 pF
| Signals | Description |
| TXC | Send Data |
| RXC | Receive Data |
| RTS | Request to Send |
| CTS | Clear to Send |
| DM | Data Mode |
| DSR | Receiver Ready |
| MC | Master Clock |
| LL | Local Loopback |
| ST | Send Timing |
| RXC | Receive Timing |
| TXC | Terminal Timing |
| MF | Mod Fault (ttl) |
| DF | Demod Fault (ttl) |
REMOTE CONTROL OPERATIONS
GENERAL
Remote control and status information are transferred via an EIA-485 (optional EIA-232) serial communications link.
Commands and data are transferred on the remote control communications link as US ASCII-encoded character strings.
The remote communications link is operated in a half-duplex mode.
Communications on the remote link are initiated by a remote controller or terminal. The modem never transmits data on the link unless it is commanded to do so.
MESSAGE STRUCTURE
The ASCII character format used requires 11 bits/character:
Commands are messages which are transmitted to a satellite modem, while responses are messages returned by a satellite modem in response to a command.
The general message structure is as follows:
A single character precedes all messages transmitted on the remote link. This character flags the start of a message. This character is:
The device address is the address of the one satellite modem which is designatedto receive a transmitted command, or which is responding to a command.
Valid device addresses are 1 to 3 characters long, and in the range of 1 to 255. Address 0 is reserved as a global address which simultaneously addresses all devices on a given communications link. Devices do not acknowledge global commands.
Each satellite modem which is connected to a common remote communications link must be assigned its own unique address. Addresses are software selectable at the modem, and must be in the range of 1 to 255.
COMMAND/RESPONSE
The command/response portion of the message contains a variable-length character sequence which conveys command and response data.
If a satellite modem receives a message addressed to it which does not match the established protocol or cannot be implemented, a negative acknowledgement message is sent in response. This message is:
END CHARACTER
Each message is ended with a single character which signals the end of the message:
|
Carriage return character for commands |
|
End braket for responses |
ERROR PERFORMANCE
| Raw BER | Command:
Response: |
<add/RBER_'cr'
>add/RBER_xm.mE-ee'cr''lf'] |
Where:
x = < or > (data modifier to indicate that the error rate is less than or greater than the returned value). m.m = 1.0 to 9.9 (error rate mantissa). ee = 1 to 99 (error rate exponent). Notes:
|
| Corrected BER | Command:
Response: |
<add/CBER_'cr'
>add/CBER_xm.mE-ee'cr''lf'] |
Where:
x = < or > (data modifier to indicate that the error rate is less than or greater than the returned value). m.m = 1.0 to 9.9 (error rate mantissa). ee = 1 to 99 (error rate exponent). Notes:
|
| Eb/N0 Status | Command:
Response |
<add/EBN0_'cr'
>add/EBN0_xnn.ndB'cr''lf'] |
Where:
x = < or > (data modifier to indicate that the Eb/N0 is less than or greater than the returned value). nn.n = 1.0 to 99.9 (Eb/N0 value). Notes:
|
| Receive Signal Level Status | Command:
Response: |
<add/RSL_'cr'
>add/RSL_xsnn.ndBm'cr''lf'] |
Where:
x = < or > (data modifier to indicate that the receive signal level is less than or greater than the returned value). s = + or - (receive signal level sign, plus or minus). nn.n = 0.0 to 99.9 (receive signal level magnitude). Notes:
|