Linx Technologies HUM-xxx-RC - Manual (Page 18)

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Triggered Transmissions
The HumRC TM Series Transceiver has a triggered transmission feature
configured through the serial interface. This causes the IU to transmit
messages as soon as a configured status line input goes high, but stop
transmissions based on configuration selection. The logic allows timed or
periodic transmissions for simple transmit-on-event conditions without an
external microcontroller or other timing logic. This reduces the required
energy and potential interference with other RF units when automatically
transmitting. The configuration options are:
1. Transmission occurs as long as input is high. This is the same as
normal, non-triggered operation.
2. Transmission lasts for the specified duration after a high-going edge,
then stops until the next high-going edge (fixed ON period).
3. Transmission starts when an input goes high, stopping when the input
goes low or the specified duration elapses, whichever occurs first. The
transmission won’t occur again until the input goes low, then high.
4. Transmission is periodic, with configured duration and interval, as long
as the trigger status line is high (periodic ON when trigger is high).
5. The transmission terminates under conditions 1–4 above, or when an
ACK is received. After an ACK no further trigger transmission occurs
until the triggered status line goes low, then high again.
6. The transmission is periodic, like condition 4, but each transmission
duration is terminated by receiving an acknowledgement.
A status input not selected for trigger timing operates normally, transmitting
as long as the input is high. It doesn’t affect the timing of periodic
transmissions, causing the two transmission requests to be logically ORed.
Receiving control messages during the off period of a triggered periodic
transmission can delay, but doesn’t cancel periodic transmission.
If there are multiple lines with edge triggers, they are logically ORed
together to generate a single trigger signal.
Please see Reference Guide RG-00104: the HumRC TM Series Command
Data Interface for details on configuring triggered transmissions.
Using the LATCH_EN Line
The LATCH_EN line sets the outputs to either momentary operation or
latched operation. During momentary operation the outputs go high for as
long as control messages are received instructing the module to take the
lines high. As soon as the control messages stop, the outputs go low.
During latched operation, when a signal is received to make a particular
status line high, it remains high until a separate activation is received to
make it go low. The transmission must stop and the module must time out
before it will register a second transmission and toggle the outputs.
When the LATCH_EN line is high, all of the outputs are latched. A serial
command is available to configure latching of individual lines.
Using the Low Power Features
The Power Down (POWER_DOWN) line can be used to completely power
down the transceiver module without the need for an external switch.
This line allows easy control of the transceiver power state from external
components, such as a microcontroller. The module is not functional while
in power down mode.
If all of the status lines are configured as inputs, then the module operates
as an IU only. It automatically goes into a low power state waiting for
one of the inputs to be asserted. This conserves battery power until a
transmission is required.