Data Sheet

UM7 DATASHEET

Rev. 1.6 – Released 1/10/2016

BINARY PACKET STRUCTURE

Data transmitted and received by the UM7 is formatted into packets containing:

1. The three character start sequence 's', 'n', 'p' to indicate the start of a new packet (i.e.

start new packet)

2. A "packet type" (PT) byte describing the function and length of the packet

3. An address byte indicating the address of the register or command

4. A sequence of data bytes, the length of which is specified in the PT byte

5. A two-byte checksum for error-detection

Table 2 - UART Serial Packet Structure

's'

'n'

'p'

packet type

(PT)

Address

Data Bytes (D0...DN-

Checksum 1

Checksum 0

All binary packets sent and received by the UM7 must conform to the format given above.

The PT byte specifies whether the packet is a read or a write operation, whether it is a batch

operation, and the length of the batch operation (when applicable). The PT byte is also used by

the UM7 to respond to commands. The specific meaning of each bit in the PT byte is given

below.

Table 3 - Packet Type (PT) byte

Has Data

Is Batch

BL3

BL2

BL1

BL0

Hidden

Table 4 - Packet Type (PT) Bit Descriptions

Bit(s)

Description

Has Data: If the packet contains data, this bit is set (1). If not, this bit is cleared (0).

Is Batch: If the packet is a batch operation, this bit is set (1). If not, this bit is

cleared (0)

5:2

Batch Length (BL): Four bits specifying the length of the batch operation. Unused

if bit 7 is cleared. The maximum batch length is therefore 2^4 = 16