Linx Technologies HUM-xxx-RC - Manual (Page 14)

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received bytes on its CDI for presentation to an external microcontroller
or computer. The data can include sensor values, battery voltage levels or
current status line states.
Automatic Responses
Two of the status lines can be configured as analog inputs to measure
voltage levels. An IU can send a Request Sample command to an RU to
respond with the analog measurements in the acknowledgement. This
allows a master unit to remotely read a sensor device without having to
place a microcontroller on the sensor.
The transceiver can be configured to respond with one or both analog
values through the CDI. Please see Reference Guide RG-00104: the
HumRC™ Series Command Data Interface for details on the CDI.
Permissions Mask
The HumRC TM Series Transceiver has a Permissions Mask in the RU that is
used to control which status lines an IU is authorized to control. With most
systems, if a transmitter is associated with a receiver then it has full control
over the receiver. With the Permissions Mask, a transmitter can be granted
authority to control only certain receiver outputs. If an IU does not have the
authority to activate a certain line, then the RU does not set it.
As an example, a factory worker can be given a fob that only opens the
door to the factory floor while the CEO has a fob that can also open
the executive offices. The hardware in the fobs is the same, but the
permissions masks are set differently for each fob.
The Pair process always sets the Permission Mask to full access. The mask
can be changed through the serial interface.
Receive Operation
During Receive Operation, the module waits for a valid control message
from an authorized (paired) transceiver. When a valid message is received,
it locks onto the hopping pattern of the transmitter and asserts the MODE_
IND line. It compares the received status line states to the Permission Mask
for the IU to see if the IU is authorized to activate the lines. The module sets
all authorized outputs to match the received states. Only status line outputs
are affected by received commands.
The RU then checks the state of the ACK_EN line and transmits an
acknowledgement packet if it is high. It looks for the next valid packet while
maintaining the frequency hopping timing. As long as an RU is receiving
valid commands from a paired IU, it will not respond to any other unit.
Once eight consecutive packets are missed, the RU is logically
disconnected from the IU and waits for the next valid packet from any IU.
Acknowledgement
A responding module is able to send an acknowledgement to the
transmitting module. This allows the initiating module to know that the
responding side received the command.
When the Responding Unit (RU) receives a valid Control Packet, it
checks the state of the ACK_EN line. If it is high the module sends an
Acknowledgement Packet.
If the Initiating Unit (IU) receives an Acknowledgement Packet that has
the same Address and Status Byte as in the Control Packet it originally
sent, then it pulls the ACK_OUT line high. A continuous stream of Control
Packets that triggers a continuous stream of Acknowledgement Packets
keeps the ACK_OUT line high.
Connecting the ACK_EN line to V
CC
causes the RU to transmit
Acknowledgement Packets as soon as it receives a valid Control Packet.
Alternately this line can be controlled by an external circuit that raises the
line when a specific action has taken place. This confirms to the IU that the
action took place rather than just acknowledging receipt of the signal.
The module can also be configured to transmit an acknowledgement with
two bytes of preset data. This feature is enabled using the Control Source
parameter through the Command Data Interface (CDI). The IU outputs the
Note: Only one RU should be enabled to transmit an acknowledgement
response for a given IU since multiple acknowledgements will interfere
with each other.