JN5139/001,515 NXP Semiconductors, JN5139/001,515 Datasheet - Page 27

• Manufacturer Part Number: JN5139/001,515
• Description: IC MCU 32BIT 56QFN
• Manufacturer: NXP Semiconductors

Specifications of JN5139/001,515

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

for transmission. During the passage of the bitstream to the modem, it passes through a CRC checksum generator
that calculates the checksum on-the-fly, and appends it to the end of the frame.
If using slotted access, it is possible for a transmission to overrun the time in its allocated slot; the Baseband
Processor handles this situation autonomously and notifies the protocol software via interrupt, rather than requiring it
to handle the overrun explicitly.
8.3.2 Reception
During reception, the radio is set to receive on a particular channel. On receipt of data from the modem, the frame is
directed into the Tx/Rx Frame Buffer where both header and frame data can be read by the protocol software. An
interrupt may be provided on receipt of the frame header. As the frame data is being received from the modem it is
passed through a checksum generator; at the end of the reception the checksum result is compared with the
checksum at the end of the message to ensure that the data has been received correctly. An interrupt may be
provided to indicate successful packet reception.
During reception, the modem determines the Link Quality, which is made available at the end of the reception as part
of the requirements of IEEE802.15.4.
8.3.3 Auto Acknowledge
Part of the protocol allows for transmitted frames to be acknowledged by the destination sending an acknowledge
packet within a very short window after the transmitted frame has been received. The JN5139 baseband processor
can automatically construct and send the acknowledgement packet without processor intervention and hence avoid
the protocol software being involved in time-critical processing within the acknowledge sequence. The JN5139
baseband processor can also request an acknowledge for packets being transmitted and handle the reception of
acknowledged packets without processor intervention.
8.3.4 Beacon Generation
In beaconing networks, the baseband processor can automatically generate and send beacon frames; the repetition
rate of the beacons is programmed by the CPU, and the baseband then constructs the beacon contents from data
delivered by the CPU. The baseband processor schedules the beacons and transmits them without CPU
intervention.
8.3.5 Security
The baseband processor supports the transmission and reception of secured frames using the Advanced Encryption
Standard (AES) algorithm transparently to the CPU. This is done by passing incoming and outgoing data through an
in-line security engine that is able to perform encryption and decryption operations on-the-fly, resulting in minimal
processor intervention. The CPU must provide the appropriate encrypt/decrypt keys for the transmission or
reception. On transmission, the key can be programmed at the same time as the rest of the frame data and setup
information.
During reception, the CPU must look up the key and provide it from information held in the header of the incoming
frame. However, the hardware of the security engine can process data much faster than the incoming frame data
rate. This means that it is possible to allow the CPU to receive the interrupt from the header of an incoming packet,
read where the frame originated, look up the key and program it to the security hardware before the end of the frame
has arrived. By providing a small amount of buffering to store incoming data while the lookup process is taking place,
the security engine can catch up processing the frame so that when the frame arrives in the receive frame buffer it is
fully decrypted.
8.4 Security Coprocessor
As well as being used during in-line encryption/decryption operations over a streaming interface and in external
memory encryption, it is also possible to use the AES core as a coprocessor to the CPU of the JN5139. To allow the
hardware to be shared between the two interfaces an arbiter ensures that the streaming interface to the AES core
always has priority, to ensure that in-line processing can take place at any time.
Some protocols require that security operations can be performed on buffered data rather than in-line. A hardware
implementation of the encryption engine significantly speeds up the processing of the contents of these buffers. The
Security Coprocessor can be accessed through software to allow the contents of memory buffers to be transformed.
© NXP Laboratories UK 2010
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