EM260-RTY Ember, EM260-RTY Datasheet - Page 17

• Manufacturer Part Number: EM260-RTY
• Description: IC ZIGBEE SYSTEM-ON-CHIP 40-QFN
• Manufacturer: Ember

Specifications of EM260-RTY

• Frequency: 2.4GHz
• Data Rate - Maximum: 250kbps
• Modulation Or Protocol: 802.15.4
• Applications: ZigBee™
• Power - Output: -32dBm ~ 3dBm
• Sensitivity: -97dBm
• Voltage - Supply: 2.1 V ~ 3.6 V
• Current - Receiving: 30mA
• Current - Transmitting: 34mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 40-QFN
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Memory Size: -
• Other names: 636-1003

4.6
Embedded Memory
The standard XAP2 microprocessor and accompanying software tools have been enhanced to create the XAP2b
microprocessor used in the EM260. The XAP2b adds data-side byte addressing support to the XAP2 by utilizing
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usage of RAM, optimized code, and a more familiar architecture when compared to the standard XAP2.
The XAP2b clock speed is 12MHz. When used with the EmberZNet stack, code is loaded into Flash memory over
the air or by a serial link using a built-in bootloader in a reserved area of the Flash. Alternatively, code may
be loaded via the SIF interface with the assistance of RAM-based utility routines also loaded via SIF.
The XAP2b in the EM260 has also been enhanced to support two separate protection levels. The EmberZNet
stack runs in System Mode, which allows full, unrestricted access to all areas of the chip, while the SPI Proto-
col and stack interface code runs in Application Mode using the EZSP. When running in Application Mode,
writing to certain areas of memory and registers is restricted to prevent common software bugs from interfer-
ing with the operation of the EmberZNet stack. These errant writes are captured and details are reported to
the developer to assist in tracking down and fixing these issues.
The EM260 contains embedded Flash and RAM memory. In addition it partitions a portion of the Flash for
Simulated EEPROM and token storage.
4.6.1
The Flash cell has been qualified for a data retention time of >100 years at room temperature. Each Flash
page size is 1024 bytes and is rated to have a guaranteed 1,000 write/erase cycles. The Flash memory has
mappings to both the program and data side address spaces.
On the program side, the Flash is always read as whole words. On the data side, the Flash memory is divided
into 16kB sections, which can be separately mapped into a Flash window for the storage of constant data and
the Simulated EEPROM. On the data side, the Flash may be read as bytes, but can only be written to one word
at a time.
4.6.2
The Ember stack reserves a section of Flash memory to provide Simulated EEPROM storage area for stack and
customer tokens. Therefore, the EM260 utilizes 8kB of upper Flash storage. This section of Flash is only acces-
sible when mapped to the Flash window in the data-side address space. Because the Flash cells are qualified
for up to 1,000 write cycles, the Simulated EEPROM implements an effective wear-leveling algorithm which
effectively extends the number of write cycles for individual tokens.
The number of set-token operations is finite due to the write cycle limitation of the Flash. It is not possible to
guarantee an exact number of set-token operations because the life of the Simulated EEPROM depends on
which tokens are written and how often.
The EM260 stores non-volatile information necessary for network operation as well as 8 tokens available to the
Host (see section 6.2.6, Tokens). The majority of internal tokens is only written when the EM260 performs a
network join or leave operation. With security turned on, a 32-bit nonce counter token is set for every 4,096
messages sent. As a simple ballpark estimate of possible set-token operations, consider an EM260 in a stable
network (no joins or leaves) not sending any messages and the Host is using only one of the 8-byte tokens
available to it. Therefore, a very rough estimate results in approximately 330,000 possible set-token opera-
tions.
The number of possible set-token calls depends on which tokens are being set, so the ratios of set-token calls
for each token plays a large factor. For example, if for every 9 times the Host sets a single App token the
nonce counter token is set (4,096 messages have been sent). A very rough estimate for the total number of
times the App token can bet set is approximately 320,000.
th
Flash Memory
Simulated EEPROM
bit of the data-side address bus to indicate byte or word accesses. This allows for more productive
120-1003-000D
EM260
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