EM3581-RTR datasheet(30/59 Pages) SILABS

30 / 59 page

EM358x

Rev 1.0

4.3.2. Transmit (Tx) Path

The EM358x Tx path produces an O-QPSK-modulated signal using the analog front end and digital baseband. The

area- and power-efficient Tx architecture uses a two-point modulation scheme to modulate the RF signal

generated by the synthesizer. The modulated RF signal is fed to the integrated PA and then out of the EM358x.

4.3.3. Integrated MAC Module

The EM358x integrates most of the IEEE 802.15.4-2003 MAC requirements in hardware. This allows the ARM®

CortexTM-M3 CPU to provide greater bandwidth to application and network operations. In addition, the hardware

acts as a first-line filter for unwanted packets. The EM358x MAC uses a DMA interface to RAM to further reduce

the overall ARM® CortexTM-M3 CPU interaction when transmitting or receiving packets.

The primary features of the MAC are:



CRC generation, appending, and checking



Hardware timers and interrupts to achieve the MAC symbol timing



Automatic preamble and SFD pre-pending on Tx packets



Address recognition and packet filtering on Rx packets



Automatic acknowledgement transmission



Automatic transmission of packets from memory



Automatic transmission after backoff time if channel is clear (CCA)



Automatic acknowledgement checking



Time stamping received and transmitted messages



Attaching packet information to received packets (LQI, RSSI, gain, time stamp, and packet status)



EEE 802.15.4-2003 timing and slotted/unslotted timing

4.3.4. Packet Trace Interface (PTI)

The EM358x integrates a true PHY-level PTI with the MAC, allowing complete, non-intrusive capture of all packets

to and from the EM358x with Ember development tools.

4.3.5. Random Number Generator

Thermal noise in the analog circuitry is digitized to provide entropy for a true random number generator (TRNG).

Ember software uses the TRNG to seed a pseudo random number generator (PRNG). The TRNG is also used

directly for cryptographic key generation.

4.4. System Modules

System modules encompass power domains, resets, clocks, system timers, power management, and encryption.

Refer to chapter 5 in the

Ember EM358x Reference Manual for more information.

4.4.1. Power domains

The EM358x contains three power domains:



An “always-on domain” containing all logic and analog cells required to manage the EM358x’s power

modes, including the GPIO controller and sleep timer. This domain must remain powered.



A “core domain” containing the CPU, Nested Vectored Interrupt Controller (NVIC), and peripherals. To save

power, this domain can be powered down using a mode called deep sleep. In the EM358x the core domain

also includes the RAM, which by default is powered down in deep sleep. An additional feature of the RAM

is that blocks of RAM cells can optionally be retained in deep sleep. This is configured using a register,

which must be written before entering deep sleep.



A “flash domain” containing the flash memory. This domain is managed by the power management

controller. During deep sleep the flash portion is completely powered down.

The preferred and recommended power configuration is to use the internal regulated power supplies to provide

power to the core and memory domains. Optionally, the on-chip regulators may be left unused, and the core and

memory domains may instead be powered from external supplies.

Refer to chapter 6 in the

Ember EM358x Reference Manual for more information.

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