XTH9-MI-128 Digi International/Maxstream, XTH9-MI-128 Datasheet - Page 46

• Manufacturer Part Number: XTH9-MI-128
• Description: MODULE RF 900MHZ 1W 115K W/MMCX
• Manufacturer: Digi International/Maxstream

Specifications of XTH9-MI-128

• Frequency: 900MHz
• Data Rate - Maximum: 230kbps
• Modulation Or Protocol: FHSS, FSK
• Power - Output: 30dBm
• Sensitivity: -110dBm
• Voltage - Supply: 3.3V, 5V
• Current - Receiving: 80mA
• Current - Transmitting: 260mA
• Data Interface: Connector, 2 x 10 Header
• Antenna Connector: MMCX
• Operating Temperature: -40°C ~ 85°C
• Package / Case: Module
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Applications: -
• Memory Size: -

XTend™ RF Module ‐ Product Manual v2.x6x
Repeater Mode
Theory of Operation
Attributes:Low power consumption
Constraints:Requires that each module have a unique MY (Source Address) parameter.
Suggestions:Insert a variable delay before repeating packets to avoid collisions 
Required Parameter Values (TX module): MD = 5 or 6, MY = unique value (can be accom-
plished by issuing the AM (Auto-set MY) and WR (Write) commands to all modules in the network)
Related Commands: Networking (MD, DT, MY, AM), Serial Interfacing (RN, PK, RO, RB)
Recommended Use: Use in networks where intermediary modules are needed to relay data to
modules beyond the transmission range of the base module.
Integrators can extend the effective range and reliability of their data radio system by forwarding
traffic through one or more repeaters. Instead of using routing tables and path discovery to estab-
lish dynamic paths through a network, the repeater system uses a sophisticated algorithm to
propagate each RF packet through the entire network.
The network supports RF packets up to 2048 bytes (when the RF data rate is set at 9600 bps (BR
= 0)). The repeater network can operate using broadcast or addressed communications for multi-
drop networks and works well in many systems with no special configuration.
When in Repeater Mode, the network repeats each message among all available modules exactly
one time. This mechanism eliminates the need for configuring specific routes.
Figure 4‐06. Repeater Network Topology
© 2010 Digi Internatonal, Inc.
Minimized interference
Each RF packet is tagged with a unique Packet ID (PID).
Each repeater will repeat a packet only once (tracked by the PID).
Increased latency and decreased throughput 
(Latency and throughput is determined by number of hops, not by number of 
repeaters. Multiple repeaters within range of source node count as one hop.)
All RF packets propagate to every module in the network (filtering rules apply).
Packet destination addresses (DT) determine which packets are sent out serial 
port and/or retransmitted.
Broadcast communications - each packet comes out every node exactly once.
Addressed communications - all modules see every packet. Only the module 
with a matching address will forward it to the DO buffer (UART IN).
System must introduce just one packet at a time to the network for transmission 
(Maximum number of bytes is determined by the PK parameter).
Each hop (H) decreases network throughput by a factor of 1/(H+1). Additional 
repeaters add network redundancy without decreasing throughput.
(based on RSSI).
Buffer any incoming serial data and delay response packet transmissions until 
previous packet has cleared out of network.
For best results, use the RO and RB commands to ensure that the RF packets 
align with the underlying protocol packets as the network can only accept one RF 
packet at a time.
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