LTP5901-IPR datasheet(25/34 Pages) LINER

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LTP5901-IPR/LTP5902-IPR

59012iprfa

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Figure 11. UART Mode 4 Transmit Flow Control

operaTion

The UART_TX_CTSn signal may be actively driven by the

companion processor when ready to receive a packet or

UART_TX_CTSn may be tied low if the companion pro-

cessor is always ready to receive a packet. After detecting

a logic ‘0’ on UART_TX_CTSn Eterna sends the entire

packet. Following the transmission of the final byte in

the packet Eterna negates UART_TX_RTSn and waits for

tTX_INTERPACKET, defined in the UART AC Characteristics

section, before asserting UART_TX_RTSn again.

For details on the timing of the UART protocol, see the

UART AC Characteristics section.

to remain inactive during the majority of the radio activity.

The autonomous MAC, provides software-independent

timing control of the radio and radio-related functions,

resultinginsuperiorreliabilityandexceptionallylowpower.

SECURITY

Network security is an often overlooked component of a

complete network solution. Proper implementation of se-

curity protocols is significant in terms of both engineering

effort and market value in an OEM product. Eterna system

solutionsprovideaFIPS-197validatedencryptionscheme

that includes authentication and encryption at the MAC

and network layers with separate keys for each mote.

This not only yields end-to-end security, but if a mote is

somehowcompromised,communicationfromothermotes

is still secure. A mechanism for secure key exchange al-

lows keys to be kept fresh. To prevent physical attacks,

Eternaincludeshardwaresupportforelectronicallylocking

devices, thereby preventing access to Eterna’s flash and

RAM memory and thus the keys and code stored therein.

TEMPERATURE SENSOR

Eterna includes a calibrated temperature sensor on chip.

The temperature readings are available locally through

Eterna’s serial API, in addition to being available via the

network manager. The performance characteristics of

the temperature sensor can be found in the Temperature

Sensor Characteristics section.

RADIO INHIBIT

The RADIO_INHIBIT input enables an external control-

ler to temporarily disable the radio software drivers (for

example, to take a sensor reading that is susceptible to

radio interference). When RADIO_INHIBIT is asserted

the software radio drivers will disallow radio operations

including clear channel assessment, packet transmits, or

packet receipts. If the radio is active in the current time

slot when RADIO_INHIBIT is asserted the radio will be

disabled after the present operation completes. For details

on the timing associated with RADIO_INHIBIT, see the

RADIO_INHIBIT AC Characteristics section.

CLI UART

The command line interface (CLI) UART port is a two

wire protocol (TX and RX) that operates at a fixed 9600

baud rate with one stop bit and no parity. The CLI UART

interfaceisintendedtosupportcommandlineinstructions

and response activity.

AUTONOMOUS MAC

Eterna was designed as a system solution to provide a

reliable, ultralow power, and secure network. A reliable

network capable of dynamically optimizing operation

over changing environments requires solutions that are

far too complex to completely support through hardware

acceleration alone. As described in the Precision Timing

section,propertimemanagementisessentialforoptimizing

a solution that is both low power and reliable. To address

theserequirementsEternaincludestheautonomousMAC,

which incorporates a coprocessor for controlling all of

the time-critical radio operations. The autonomous MAC

provides two benefits: first, preventing variable software

latency from affecting network timing and second, greatly

reducing system power consumption by allowing the CPU

59012IPR F11

UART_TX

BYTE 0

BYTE 1

UART_TX_CTSn

UART_TX_RTSn

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