Moog Crossbow NAV440 Series - Manual (Page 60)

e 60 NAV440 User Manual
7430‐0131‐01 Rev. F
Pag
Descriptor Description Size (bytes) Comment Range
F4 Floating Point 4 IEEE754 Single
ion Precis
‐1*2^127 to 2^127
SN String N ASCII
Packet Format
ll of the Input and Output packets, except the Ping command, conform to the following structure: A
0x5555 <2‐byte packet type (U2)> <payload byte‐length (U1)> <variable length payload> <2‐byte CRC (U2)>
The Ping Command does not require a CRC, so a 440Series unit can be pinged from a terminal emulator. To Ping a
Series 440unit, type the ASCII string ‘UUPK’. If properly connected, the 440 Series unit will respond with ‘PK’. All
other communications with a Series 440unit require the 2‐byte CRC.
NOTE: A Series 440unit will also respond to a ping command using the full packet formation with payload 0 and
correctly calculated CRC. Example: 0x5555504B009ef4.
Packet Header
The packet header is always the bit pattern 0x5555.
Packet Type
The packet type is always two bytes long in unsigned short integer format. Most input and output packet types can
be interpreted as a pair of ASCII characters. As a semantic aid consider the following single character acronyms:
Table 12 Character Acronyms
Acronym Description
P Packet
F Fields: Refers to Fields which are settings or data contained in the unit
E EEPROM Refers to factory data stored in EEPROM
R Read: Reads default non‐volatile fields
G Get: Ge s current volatile fields or settings t
W Write: Writes default non‐volatile fields. These fields are stored in non‐volatile memory and
determine the unit’s behavior on power up. Modifying default fields take effect on the next power
up and thereafter.
S Set: Sets current volatile fields or settings. Modifying current fields will take effect immediately by
modifying internal RAM and are lost on a power cycle.