Specifications

encryption key. Your encryption key should be complex and difficult to guess, and it should avoid
repeated characters when possible.
An encryption key must be exactly 16 bytes (128 bits) long to be valid. This parameter has no effect
unless NV parameter #50 is also set to enable encryption.
Even if NV parameter #50 is set for AES-128 encryption and parameter 51 has a valid encryption key,
communications will not be encrypted unless the node is loaded with a SNAP firmware image that
supports AES-128 encryption. Firmware images supporting AES-128 encryption will have “AES” in
their filenames.
Refer also to function getInfo() in the SNAPpy API section.
ID 52 – Lockdown
If this parameter is 0 (or never set at all), access is unrestricted. You can freely upload new scripts.
If you set this parameter to 1, and then reboot the node (as you always have to do for any NV
Parameter change to take effect), then the system enters a “lockdown” mode where over-the-air script
erasure or upload is disallowed.
Values other than 0 or 1 are reserved for future use, and should not be used.
While in “lockdown” mode, you also cannot write to NV parameter #52 over-the-air (in other words,
you cannot bypass the lockdown by remotely turning it off).
Even in this mode, you can still perform all operations (including script upload or erasure) over the
local Packet Serial link (assuming one is available). The lockdown only applies to over the air access.
If you have disabled your UARTs and set this parameter, you will have to use Portal to reset your
factory parameters to regain control of your node script.
ID 53 – Maximum Loyalty
This parameter, expressed in milliseconds, is valid only for the FHSS (frequency-hopping) firmware
for the Si100x (including the RF300). It will be ignored on all other platforms.
After transmitting or receiving on a particular frequency, a node will wait for a signal on the next
expected frequency for the duration of the loyalty period before it begins scanning all frequencies for
additional communications.
If a node has transmitted or received a message and its loyalty period has not expired before it
transmits its next message, it will transmit with a shorter preamble, expecting that the receiving node
is listening on the appropriate channel within its own loyalty period. The shorter preamble allows for
faster communications, at the risk of packets being missed by nodes that are not currently “loyal” to an
expected channel.
If you adjust the loyalty period, all nodes in the network should be set to the same value. Setting the
value to 0 means that no node will ever expect a loyalty period: all broadcasts will begin with a full
Page 104 of 202 SNAP Reference Manual Document Number 600-0007K