Data Sheet

UM7 DATASHEET
Rev. 1.6 – Released 1/10/2016
32
1
Hidden: If set, then the packet address specified in the “Address” field is a
“hidden” address. Hidden registers are used to store factory calibration and filter
tuning coefficients that do not typically need to be viewed or modified by the user.
This bit should always be set to 0 to avoid altering factory configuration.
0
Command Failed (CF): Used by the autopilot to report when a command has failed.
Must be set to zero for all packets written to the UM7.
The address byte specifies which register will be involved in the operation. During a read
operation (Has Data = 0), the address specifies which register to read. During a write operation
(Has Data = 1), the address specifies where to place the data contained in the data section of
the packet. For a batch read/write operation, the address byte specifies the starting address of
the operation.
The "Data Bytes" section of the packet contains data to be written to one or more registers.
There is no byte in the packet that explicitly states how many bytes are in this section because
it is possible to determine the number of data bytes that should be in the packet by evaluating
the PT byte.
If the Has Data bit in the PT byte is cleared (Has Data = 0), then there are no data bytes in the
packet and the Checksum immediately follows the address. If, on the other hand, the Has Data
bit is set (Has Data = 1) then the number of bytes in the data section depends on the value of
the Is Batch and Batch Length portions of the PT byte.
For a batch operation (Is Batch = 1), the length of the packet data section is equal to 4*(Batch
Length). Note that the batch length refers to the number of registers in the batch, NOT the
number of bytes. Registers are 4 bytes long.
For a non-batch operation (Is Batch = 0), the length of the data section is equal to 4 bytes (one
register). The data section lengths and total packet lengths for different PT configurations are
shown below.
Table 5 - Packet Length Summary
Has
Data
Is Batch
Data Section Length
(bytes)
Total Packet Length (bytes)
0
NA
0
7
1
0
4
11
1
1
4*(Batch Length)
7 + 4*(Batch Length)