User's Manual

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16
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RF Digital Corp.
9/2/2010 12:02 PM
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RFDP8
RFDANT
RFD21743
Eval Board
RFD21773
Modes 6 – Receiver with Logic Output (20ms hang-time)
Pin # Pin Label Direction Function
13 +V Input +V Power
10 GND Input Ground
16 Mode Select 0 Input Tie to GND
17 Mode Select 1 Input Tie to +V
3 Mode Select 2 Input Tie to +V
4 Not Used Output Leave open, not used.
5 OUT1 Output Active high switch output #1, 20 millisecond hang-time.
6 OUT2 Output Active high switch output #2, 20 millisecond hang-time.
7 OUT3 Output Active high switch output #3, 20 millisecond hang-time.
Modes 7 – Receiver with Logic Output (Network) (20ms hang-time)
Pin # Pin Label Direction Function
13 +V Input +V Power
10 GND Input Ground
16 Mode Select 0 Input Tie to +V
17 Mode Select 1 Input Tie to +V
3 Mode Select 2 Input Tie to +V
4 Learn / Status I/O Pulse high to enter learn mode and LED Learn Status Output.
5 OUT1 Output Active high switch output #1, 20 millisecond hang-time.
6 OUT2 Output Active high switch output #2, 20 millisecond hang-time.
7 OUT3 Output Active high switch output #3, 20 millisecond hang-time.
In modes 4 through 7, the module is always in receiving mode.
The receiver drives its outputs to match the values received in a packet from a transmitter. This allows up to 8
possible (2
3
) combinations on the receiver’s outputs.
Since a transmitter does not send any data when all of its inputs are low, there must be a mechanism for turning
off the receiver’s outputs in the absence of data. When Mode Select 1 is pulled to GND, the receiver will maintain
its output state for 500ms or until it receives new data, whichever comes first. The 500ms is referred to as the
“hang time,” or the time that the outputs will “hang” in the absence of new data. If Mode Select 1 is pulled to +V,
the hang time is 20ms.
Hang time is a trade-off between latency and resiliency to packet loss. With all RF systems sometimes a packet
will be lost, especially as the distance between the transmitter and the receiver grows. If an output is connected
to a relay driver, packet loss will result in chattering on the relay, which will not have good results. The 500ms
hang time is perfect for applications like a keyless entry system or a garage door opener.
For faster switching to the “all off” state, the 20ms hang time is preferred. Since a transmitter sends new data
every 15ms, the time delay to turn off all outputs is only 5ms more than to update the outputs to a different state
where at least one of them is still driven high.