User's Manual

Company Confidential 60 Raveon Technologies Corp.

factory default duration of the pause it looks for is 20mS, but the user may

hange this to over values using the ATR3 xxx command, where xxx is in

milliseconds.

Busy-Channel Lock Out

If your system operation require the M7 modem to monitor-before-transmit, of if

you do not want the M7 to transmit on a channel that is busy, you can enable

“Busy-Channel-Lockout”, using the ATBC 1 command. ATBC 0 disables BCL,

and thus the modem will transmit whenever it has data to send out. The factory-

default is BCL disabled. Use caution when enabling it, as a CW interferer, PC

with poor shielding, or some other source of RF can stop the modem from

transmitting. The threshold where the M7 senses RF carrier, and determines

that the channel is busy is set by the ATRA command. This is factory calibrated

to an equivalent RF level of approximately -110dBm.

6.4. Data Reception

When the modem receives data over the radio, it checks it for errors, and if it is

error-free, it will send it out the serial port. Again, the serial port may be set to

any baud rate the user wishes, and the radio receiver and transmitter will

continue to operate independently of the baud rate.

When the modem receives a signal, it will assert the CD hardware signal on the

RS-232 serial port if it was configured to do so.

In general, the slower the over-the-air data rate, the easier it is for the modem to

receive the signal, and thus the more communication range the radio will have.

M7 modems have a unique switched-filter along with digital signal processing,

that gives them more range a lower data rates. See Section 9.1 Setting the

Over-The-Air Data Rate for more information about choosing the over-the-air

data rate.

6.5. Addressing (Packetized Mode only)

Addressing Basics

One of the more powerful aspects of the M7 modem is its addressing scheme.

Incorporating addressing in the modem allows multiple radio systems on the

same frequency to co-exist, and not interfere with each other. Also, some user

application cannot tolerate receiving data that was not intended for it, and by

setting the addresses in the modems properly, the system can be configured to

allow reception of only data intended for the recipient.

If addressing is not needed or desired, it can be turned off so that all modems

receive data from all other modems, and all modems can talk to all other

modems.

Each M7 contains a 16 bit address, called its Unit Address, and is represented as

a 4 digit hexadecimal number. M7 address may be any number between 0000

and FFFF, which is effectively 65,535 different addresses. Every M7 has a Unit

Address programmed into it, as well as the ID of the unit it will send data to. The