RXM-433-RM Linx Technologies Inc, RXM-433-RM Datasheet - Page 8

• Manufacturer Part Number: RXM-433-RM
• Description: RECEIVER RF 433MHZ
• Manufacturer: Linx Technologies Inc
• Series: RMr

Specifications of RXM-433-RM

• Frequency: 433MHz
• Sensitivity: -100dBm
• Data Rate - Maximum: 10 kbps
• Modulation Or Protocol: ASK, OOK
• Applications: ISM, Garage Door Openers, RKE
• Current - Receiving: 14mA
• Data Interface: PCB, Through Hole
• Antenna Connector: Through Hole
• Voltage - Supply: 3.9 V ~ 9 V
• Operating Temperature: -10°C ~ 50°C
• Package / Case: 7-SIP
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Features: -
• Memory Size: -

THE DATA OUTPUT
USING THE DETECT OUTPUT
Page 8
A CMOS-compatible data output is available on pin 7. This output is normally
used to drive a digital decoder IC or a microprocessor which is performing the
data decoding.The data slicer in the receiver module is designed to accept data
with a wide range of pulse widths and mark:space ratios (see specification table
for limiting values).The data slicer has a 10 mS initial settling time. During this
settling period the data may be corrupt at the data output.
It is important to recognize that the data output pin is unsquelched and
unqualified.This is done to maximize the sensitivity of the receiver and to allow
the user complete control over data qualification methods. The designer must
take into account that the data output will not hold a DC level in the absence of
a transmitted carrier. The output may “hash”, that is toggle randomly on noise or
other signals present in the environment.
In order to assure a reliable and robust link the designer must understand that a
wireless link has issues of timing and error not frequently found in a wired
environment. Since these issues are common to any RF link many simple
methodologies exist for dealing with them. Common approaches would include
p r e a m ble qualification, error detection, and carrier detect or squelch
implementation.
Pin 3 of the module may be used in several ways:
1.
output for normal operation.
2.
outputs (both go to 0 Volt).
3.
in the absence of a transmitter carrier. Most applications will be unaffected by this
condition or the condition can be resolved in software. In instances where it is
necessary to qualify the data, the carrier detect output can be used for
qualification. The carrier detect pin (pin 3) is not directly suitable for carrier
indication as it has a limited swing from Vcc-.8V with no carrier to Vcc-.3 volts
with a strong carrier. Therefore some external circuitry is necessary to provide a
logic level output.
Many different circuits can be implemented to derive a logic level output from the
small available voltage swing. Figure 9 demonstrates one such simple circuit.
This circuit works by taking advantage of the BC558 transistor’s characteristics.
The transistor, as with many PNP transistors, will turn “on”when its base is more
than .7V below the collector voltage. When a carrier is present, the base voltage
is only .3V below VCC (and the collector voltage) and the transistor is “off” forcing
the “detect” output low through the 47K resistor. When a carrier is not present,
the base voltage is .8V below VCC, and the transistor will turn “on”, causing the
“detect” output to go high.
The usefulness of the carrier detect pin is not limited to data qualification.It may
also be used for duty-cycle power-saving control in portable equipment where
battery life is a problem.Once the designer has added the external components
necessary to derive a logic level detect signal the receiver can be periodically
turned on and checked for a valid carrier. If a carrier is received the user’s
Pulled up to pin 5 (Vcc) with a 47 K
Pulled down to 0 Volts with a 47 K
The data output of the receiver is not qualified, therefore “hashing”is present
disables (mutes) the AF and DATA
resistor unmutes the AF and DATA