Digi XTend User Manual page 60

TX Packet (16-bit address) Frames
Identifies the UART data frame for the host to
correlate with a subsequent ACK (acknowledgement).
Setting Frame ID to '0' will disable response frame.
Example: TX Packet API Frames
Byte 1 Bytes 2-3
0x7E 0x00 0x08
Start Delimiter Length*
* Length [Bytes] = API Identifier + Frame ID + Option + RF Data
** "R" value was arbitrarily selected
TX (Transmit) Status
API Identifier Value: 0x89
When a TX Request is completed, the module sends a TX Status message. This message will indicate if the packet was
transmitted successfully or if there was a failure.
TX Status Frames
Start Delimiter
0x7E
Identifies UART data frame being reported.
Note: If Frame ID = 0 in the TX Request, no
AT Command Response will be given.
Note "STATUS = 1" occurs when all retries are expired and no ACK is received.
"STATUS = 3" occurs when a packet is purged due to a 'Polled Remote' not receiving a poll.
RX (Receive) Packet: 16-bit address
API Identifier Value: 0x81
When the module receives an RF packet, it is sent out the UART using this message type.
XTend RF Module User Guide
Start Delimiter Length
0x7E MSB LSB
API Identifier
0x01
Frame ID (Byte 5)
Byte 4 Byte 5
0x01 R (0x52)
API Identifier Frame ID**
Length Frame Data
MSB LSB API-specific Structure
API Identifier Identifier-specific Data
0x89
Frame ID (Byte 5)
Frame Data Checksum
API-specific Structure 1 Byte
Identifier-specific Data
cmdData
Destination Address (Bytes 6-7)
MSB first, LSB last.
Broadcast = 0xFFFF
Bytes 6-7
0xFFFF
Destination Address
Checksum
1 Byte
cmdData
Status (Byte 6)
0 = Success
1 = No ACK (Acknowledgement) received
Options (Byte 8) RF Data (Byte(s) 9-n)
0 = Standard
Up to 2048 Bytes per packet
1 = Disable ACK
Byte 8 Bytes 9-11
0x00 1 (0x31) 2 (0x32) 3 (0x33)
Option RF Data
API operation
Byte 12
0x18
Checksum
60