Digi XBee 3 ZigBee User Manual

API Operation API frame format
Digi XBee® 3 Zigbee® RF Module
239
Start delimiter Length Frame type
Frame Data
Checksum
Data
7E 00 0F 17 01 00 7D 33 A2 00 40 AD 14 2E FF FE 02 4E 49 6D
The length field has a two-byte value that specifies the number of bytes in the frame data field. It does
not include the checksum field.
Length field
The length field is a two-byte value that specifies the number of bytes contained in the frame data
field. It does not include the checksum field.
Frame data
This field contains the information that a device receives or will transmit. The structure of frame data
depends on the purpose of the API frame:
Start delimiter Length
Frame data
ChecksumFrame type
Data
1 2 3 4 5 6 7 8 9 ... n n+1
0x7E MSB LSB
APIframe type
Data
Single byte
n Frame type is the API frame type identifier. It determines the type of API frame and indicates
how the Data field organizes the information.
n Data contains the data itself. This information and its order depend on the what type of frame
that the Frame type field defines.
Multi-byte values are sent big-endian.
Calculate and verify checksums
To test data integrity, the device calculates and verifies a checksum on non-escaped data.
To calculate the checksum of an API frame:
1. Add all bytes of the packet, except the start delimiter 0x7E and the length (the second and
third bytes).
2. Keep only the lowest 8 bits from the result.
3. Subtract this quantity from 0xFF.
To verify the checksum of an API frame:
1. Add all bytes including the checksum; do not include the delimiter and length.
2. If the checksum is correct, the last two digits on the far right of the sum equal 0xFF.
Example
Consider the following sample data packet: 7E 00 08 08 01 4E 49 58 42 45 45 3B

Digi XBee 3 ZigBee Specifications

General

Brand	Digi
Model	XBee 3 ZigBee
Category	Control Unit
Language	English