Data Sheet

UM7 DATASHEET

Rev. 1.6 – Released 1/10/2016

Note that if a packet is a batch operation, the batch length must be greater than zero.

The two checksum bytes consist of the unsigned 16-bit sum of all preceding bytes in the packet,

including the packet header.

Read Operations

To initiate a serial read of one or more registers aboard the sensor, a packet should be sent to

the UM7 with the "Has Data" bit cleared. This tells the device that this will be a read operation

from the address specified in the packet's "Address" byte. If the "Is Batch" bit is set, then the

packet will trigger a batch read in which the "Address" byte specifies the address of the first

In response to a read packet, the UM7 will send a packet in which the "Has Data" bit is set, and

the "Is Batch" and "Batch Length" bits are equivalent to those of the packet that triggered the

read operation. The register data will be contained in the "Data Bytes" section of the packet.

Write Operations

To initiate a serial write into one or more registers aboard the sensor, a packet should be sent

to the UM7 with the "Has Data" bit set. This tells the device that the incoming packet contains

data that should be written to the register specified by the packet's "Address" byte. If a batch

write operation is to be performed, the "Is Batch" bit should be set, and the "Batch Length" bits

should indicate the number of registers that are to be written to.

In response to a write packet, the UM7 will update the contents of the specified register(s) with

the contents of the data section of the packet. It will then transmit a COMMAND_COMPLETE

packet to indicate that the write operation succeeded. A COMMAND_COMPLETE packet is a

packet with PT = 0 (no data, no batch) and with an address matching the address of the register

to which the write operation was made, or the start address of the write operation if this was a

batch write.

Note that the COMMAND_COMPLETE packet is equivalent to a packet that would cause the

autopilot to initiate a read operation on the address to which data was just written. Since the

packet is going from the sensor to the host, however, its meaning is different (it would not

make sense for the autopilot to request the contents of one of its registers from an external

host).