Specifications

For RF100 SNAP Engines, the PA feature bit (0x10) should only be set on “RFET” units. Setting this

bit on a “RFE” board will not harm the SNAP Engine, but will actually result in lower transmit power

levels (a 20-40% reduction). The bit should be set for RF200 SNAP Engines, as well.

The external power-down bit (0x20) should be set on units that need to power down external hardware

before going to sleep, and power it back up after they awake. This bit is not modified when you reset

parameters to factory defaults.

The alternate clock source bit (0x40) modifies which timer is used on SNAP modules that have

multiple timers available, for increased PWM flexibility. See the details about the individual platform

builds to determine if an alternate clock is available on your platform.

The DS_AUDIO enable bit (0x80) enables I

S audio communications over the SNAP network on

platforms that support it. Refer to each platform’s details to determine whether this capability is

available.

The second CRC bit (0x100) enables a second CRC packet integrity check on platforms that support it.

Setting this bit tells the SNAP node to send a second cyclical redundancy check (using a different

CRC algorithm) on each RPC or multicast packet, and require this second CRC on any such packet it

receives. This reduces the available data payload by two bytes (to 106 bytes for an RPC message, or

109 bytes for a multicast message), but provides an additional level of protection against receiving

(and potentially acting upon) a corrupted packet. The CRC that has always been a part of SNAP

packets means that there is a one in 65,536 chance that a corrupted packet might get interpreted as

valid. The second CRC should reduce this to a less than a one in four billion chance.

If you set this bit for the second CRC, you should set it in all nodes in your network, and enable the

feature in your Portal preferences or as a feature bit in your SNAP Connect NV parameters. A node

that does not have this parameter set will be able to hear and act on messages from a node that does

have it set, but will not be able to communicate back to that node. Not all platforms support this

second CRC. Refer to each platform’s details to determine whether this capability is available. This

feature was added in release 2.4.20.

The world-wide bit (0x200) enables an alternate set of power restrictions on platforms that support it.

For example, an SM700 module will normally enforce FCC (US) Transmit Power Restrictions. If the

0x0200 Feature Bit is set, the SM700 will instead enforce ETSI restrictions.

Binary notations are provided here for clarity. You should specify the parameter value using the

appropriate hexadecimal notation. For example, 0x001F corresponds to 0b0000,0000,0001,1111.

ID 12 – Default UART

This controls which UART will be pre-configured for Packet Serial Mode.

Normally the UART related settings would be specified by the SNAPpy scripts uploaded into the

node. This default setting has been implemented to handle nodes that have no scripts loaded yet.

These defaults are overridden when needed!

SNAP Reference Manual Document Number 600-0007K Page 95 of 202