background image

MHX-900 Operating Manual: Appendix F Glossary

29

F. Glossary

Terminology Used in the MHX-900 Operating Manual

Asynchronous communications

  

A method of

telecommunications in which units of single bytes
of data are sent separately and at an arbitrary time
(not periodically or referenced to a clock).  Bytes
are “padded” with start and stop bits to distinguish
each as a unit for the receiving end, which need
not be synchronized with the sending terminal.

Attenuation

  

The loss of signal power through

equipment, lines/cables, or other transmission
devices.  Measured in decibels (dB).

Bandwidth

  

The information-carrying capacity of a

data transmission medium or device, usually
expressed in bits/second (bps).

Baud

  

Unit of signaling speed equivalent to the

number of discrete conditions or events per
second.  If each signal event represents only one
bit condition, then baud rate equals bits per
second (bps) – this is generally true of the serial
data port, so 

baud

 and 

bps

 have been used

interchangeably in this manual when referring to
the serial port; this is not always the case during
the DCE-to-DCE communications, where a
number of modulation techniques are used to
increase the bps rate over the baud rate.

Bit

  

The smallest unit of information in a binary

system, represented by either a 1 or 0.
Abbreviated “b”.

Bits per second

  

(b/s or bps) A measure of data

transmission rate in serial communications.  Also
see 

baud

.

Byte

  

A group of bits, generally 8 bits in length.  A

byte typically represents a character of data.
Abbreviated “B”.

Characters per second

  

(cps) A measure of data

transmission rate for common exchanges of data.
A character is usually represented by 10 bits: an 8-
bit byte plus two additional bits for marking the
start and stop.  Thus, in most cases (but not
always), 

cps

 is related to 

bits per second (bps)

 by

a 1:10 ratio.

CRC

  

(Cyclic Redundancy Check) An error-detection

scheme for transmitted data.  Performed by using
a polynomial algorithm on data, and appending a
checksum to the end of the packet.  At the

receiving end, a similar algorithm is performed
and checked against the transmitted checksum.

Crossover cable

  

(Also known as rollover, null-

modem, or modem-eliminator cable) A cable
which allows direct DTE-to-DTE connection
without intermediate DCEs typically used to
bridge the two communicating devices.  Can also
be used to make cabled DCE-to-DCE connections.
The name is derived from “crossing” or “rolling”
several lines, including the TX and RX lines so
that transmitted data from one DTE is received on
the RX pin of the other DTE and vice-versa.

Data Communications Equipment

  

(DCE, also

referred to as Data Circuit-Terminating
Equipment, Data Set)  A device which facilitates a
communications connection between 

Data

Terminal Equipment

 (DTEs).  Often, two or more

compatible DCE devices are used to “bridge”
DTEs which need to exchange data.  A DCE
performs signal encoding, decoding, and
conversion of data sent/received by the DTE, and
transmits/receives data with another DCE.
Common example is a modem.

Data Terminal Equipment

  

(DTE) An end-

device which sends/receives data to/from a DCE,
often providing a user-interface for information
exchange.  Common examples are computers,
terminals, and printers.

dBm

  

Stands for “Decibels referenced to one

milliwatt (1 mW)”.  A standard unit of power
level commonly used in RF and communications
work.  

n

 dBm is equal to 10

(n/10)

 milliwatt, so

0dBm = 1mW, -10dBm = 0.1mW, -20dBm =
0.01mW, etc.

DCE

  

See

 Data Communications Equipment

.

DTE

  

See

 Data Terminal Equipment

.

Flow Control

  

A method of moderating the

transmission of data so that all devices within the
communications link (DTEs and DCEs) transmit
and receive only as much data as they can handle
at once.  This prevents devices from sending data
which cannot be received at the other end due to
conditions such as a full buffer or hardware not in
a ready state.  This is ideally handled by hardware
using flow-control and handshaking signals, but

Содержание MHX-900

Страница 1: ...mplete However the company reserves the right to make changes or enhancements to the manual and or the product described herein at any time and without notice Furthermore Microhard Systems Inc assumes...

Страница 2: ......

Страница 3: ...ration 10 W Write Configuration to memory 10 Sxxx Read S register value 10 Sxxx yyy Set S register value 10 3 2 Command Result Codes 10 3 3 S Registers 11 S Register 2 Escape Code 11 S Register 3 CR C...

Страница 4: ......

Страница 5: ...ndability The MHX 900 module s versatility makes it the ideal solution for applications ranging from office productivity to industrial data control and acquisition While a pair of MHX 900 modules can...

Страница 6: ...ins instructions suggestions and information which will help you set up and achieve optimal performance from your equipment using the MHX 900 module It is assumed that users of the MHX 900 module have...

Страница 7: ...n new or existing designs n Relatively small footprint for the MHX 900 module e g 2 1 W x 3 5 L x 0 8 H on the OEM PCB n Serial port and control signals from the host microprocessor See sample applica...

Страница 8: ...MHX 900 module s digital electronics To simplify the OEM design the Radio VCC can be connected to the Logic VCC Maximum current while transmitting is approx 100 mA DC GND These are the Ground supply...

Страница 9: ...minimum configuration requirements for point to point and point to multipoint are summarized below These requirements will get you started and only ensure that a link can be established but do not ne...

Страница 10: ...iguration into non volatile memory and are therefore retained even after powering down Each item and the settable parameters within the modem configuration are described in detail in Chapter 3 Configu...

Страница 11: ...er command 3 Issuing the online command You can place the modem into Command Mode either by 1 Sending the escape sequence 2 Toggling the DTR line Note When the connection is lost to the remote modem t...

Страница 12: ...able commands denotes standard factory settings A Answer The A command causes the modem to attempt to connect with another remote modem D Dial Using the D command the modem will set itself for master...

Страница 13: ...d load stored configuration The Z command resets the modem and loads the stored configuration C DCD Data Carrier Detect The C command controls the modems DCD output signal to the host microprocessor T...

Страница 14: ...e modem s non volatile memory Sxxx Read S register value This command causes the modem to display the current setting of S register xxx Sxxx yyy Set S register value see section on S Registers This co...

Страница 15: ...43 S Register 3 CR Control Code This register contains the ASCII value of the carriage return character This is the character that is used to end the command line and is also the character that appear...

Страница 16: ...edgements along with CRC error checking ensure that data is passed through exactly once and that the data is not corrupted 3 Master Point to Multipoint In a point to multipoint network one unit should...

Страница 17: ...reliably at 115200 S Register 103 Wireless Link Rate The Wireless Link Rate is the speed and optimization method for which modems will communicate over the RF link The allowable settings are 1 Turbo...

Страница 18: ...rently in close proximity it is suggested that an atypical value be chosen perhaps something meaningful yet not easily selected by chance or coincidence Default is 0 S Register 105 Unit Address In poi...

Страница 19: ...f high gain directional antennas are placed high above ground level and are in direct line of sight 10 mW 200 500 ft indoors 8 15 km outdoors 100 mW 400 800 ft indoors 15 25 km outdoors 1000 mW 1 W Ty...

Страница 20: ...he following settings are available S Register 111 Minimum Size This setting has a range of 0 to 255 and defines the number of bytes to accumulate from the DTE before transmitting a packet Setting thi...

Страница 21: ...ximum Size 255 S113 Retransmissions 255 S114 Address Header Disabled S Register 111 Minimum Size The Minimum Size parameter prevents the Slave from sending data until it has buffered a minimum number...

Страница 22: ...Maximum Packet Size includes the Address Header For example if the Maximum Packet Size is set to 128 and the Text Address Header option is selected then the Master will tell the Slave to send a maxim...

Страница 23: ...mand mode V View Configuration W Write configuration to memory Sxx Read S register value Sxx yy Set S register value Result Codes 0 OK 1 CONNECT 2 RING 3 NO CARRIER 4 ERROR 8 NO ANSWER 10 CONNECT 2400...

Страница 24: ...20 MHX 900 Operating Manual Appendix A Modem Command Summary...

Страница 25: ...rted TTL low by the DTE to inform the modem that it is alive and ready for communications SG Signal Ground Provides a ground reference for all signals transmitted by both DTE and DCE DSR Data Set Read...

Страница 26: ...22 MHX 900 Operating Manual Appendix B Serial Interface...

Страница 27: ...Y RESULT On this implementation the onboard SCI of the PIC 16C74 is directly connected pins 22 and 23 of the MHX 900 The bi directional Port D is used for asserting or monitoring control signals from...

Страница 28: ...24 MHX 900 Operating Manual Appendix C Sample Schematic Diagram...

Страница 29: ...The same Hopping Interval S Register S109 value must be selected for both modems n The same Encryption Key S Register S107 value must be selected for both modems The master can now attempt to synchron...

Страница 30: ...26 MHX 900 Operating Manual Appendix D Modem Setup Overview...

Страница 31: ...stained in intelligent asymmetrical full duplex transmission mode Communications Range Up to 30 kilometres 19 miles line of sight Power Requirements 4 75 to 5 5 VDC Power Consumption 5500 mA at 1 W tr...

Страница 32: ...28 MHX 900 Operating Manual Appendix E Technical Specifications...

Страница 33: ...detection scheme for transmitted data Performed by using a polynomial algorithm on data and appending a checksum to the end of the packet At the receiving end a similar algorithm is performed and chec...

Страница 34: ...device RS 232 Recommended Standard 232 more accurately RS 232C or EIA TIA 232E Defined by the EIA a widely known standard electrical and physical interface for linking DCEs and DTEs for serial data co...

Отзывы: