XR18W750 Datasheet, PDF (7/44 Pages) Exar Corporation – WIRELESS UART CONTROLLER

XR18W750
REV. 1.0.0
WIRELESS UART CONTROLLER
1.4.1 XR18W753 RF Transceiver
The XR18W753 is an RF Transceiver with frequency ranges of 868MHz - 954MHz and a data rate of 250kbps.
All of the Physical Layer Management Entity (PLME) registers to configure and control the XR18W753 can be
accessed via the I²C interface. See the XR18W753 datasheet for complete details.
1.4.2 External EEPROM
An external I²C EEPROM is required to store the firmware for the 8051 microprocessor and the parameters of
the Wireless UART chipset. The I²C EEPROM must have at least 32KB of memory.
1.4.2.1 EEPROM Parameters
The table below describes all of the parameters that are stored in the external I²C EEPROM.
TABLE 1: EEPROM PARAMATERS
PARAMETER
BYTES
DESCRIPTION
Source ID
4
These bytes are sent in the packet preamble to identify who is sending the
packet in P2P mode.
Destination ID
4
These bytes are sent in the packet preamble to identify who is to receive
the packet in the P2P mode.
Baud Rate
4
These 4 bytes store the default baud rate that the UART will be initialized
to during the next power-up.
Communication Mode
1
This parameter selects the communication mode: P2P, P2M, Broadcast.
Channel Number (Frequency)
1
This byte stores the default or last used channel frequency of the
XR18W753 RF Transceiver.
Number of Retries
1
This byte stores the number of times to re-transmit a packet when an ACK
is not received in P2P mode before giving up.
Group ID
1
These bytes are compared by the recipient when a broadcast packet has
been received.
Power Level
1
This byte stores the default power level for the XR18W753.
XR18W753 address
1
This byte stores the I²C address of the XR18W753.
Autobaud Detect
1
This byte selects whether the device has the Autobaud Detect feature
enabled upon power-up.
Power-up Mode
1
This byte selects whether the device powers up in the command or the
data mode.
AES Security Key
16
This parameter is used for as the encoding/decoding key in the AES
Engine.
2.0 COMMUNICATION MODES
2.1 Point-to-Point
Point-to-point communication is similar to two UARTs communicating via RS-232 or RS-422. The differences
being that the communication is now wireless and half-duplex. Each time a wireless data packet is
transmitted, the Wireless UART chipset waits until an ACK is received. If an ACK has not been received, the
Wireless UART chipset will re-transmit the packet. The Wireless UART chipset will attempt to re-transmit the
packet until the specified number of retries has been reached.
In this communication mode, the packet will only be received and an ACK will be sent if the two Wireless UART
chipsets are configured for the same frequency, with matching AES security keys and the Destination ID of the
packet matches the Source ID of the Wireless UART chipset.
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