Streaming extension ofGen2 communication
protocolJULY 7, 2021
BACKSCATTER COMMUNICATION RESEARCH CONSORTIUM
KEIO UNIVERSITY

Streaming extension of Gen2 communication protocol

1 Overview
This note proposes an extension of ISO/IEC 18000-63 (2015) specification (hereinafter,
Gen2)[1] or a new stream of protocol to enable concurrent sensor data streaming frommultiple radio frequency (RF) tags with the multiple subcarrier multiple access (MSMA)
technology [2] using backscatter technology. The basic composition of the MSMA systemcomprises a reader/writer (hereinafter, reader) and a group of multiple backscatter tags
(Figure 1).

MSMA tagRFIC
sensorbackscatter
SPI+Power Supply

commands / power

TX
RX

Reader/Writer

MSMA
tag

MSMA
tag

Figure 1 MSMA system composition

As shown in Figure 1, an MSMA tag comprises an RF integrated circuit (RFIC), which handles
the communication with the reader, and a sensor connected to RFIC through, for example,
the serial peripheral interface (SPI) in our implementation. The power to the sensor can beprovided by RFIC, which is the SPI master, and the sensor is an SPI slave.

The concurrency in MSMA in its sensor streaming stage is realized by simultaneously using
multiple subcarriers. The Miller encoded subcarrier is extensively used in commercial RFID
systems with Gen2 protocol. However, only one tag responds to its reader at a time. In
MSMA, each tag in the view field of the reader is assigned a narrowband subcarrier channel
by the reader, then the sensor data can be concurrently streamed using the dedicatedsubcarriers. An overview of the communication protocol and MSMA tags is explained in thenext subsection.

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Streaming extension of Gen2 communication protocol

1.1 Communication protocol
Each MSMA tag should be capable of inventory, read, and write operations in Gen2.
In addition to the standardized communication protocol, the MSMA tag can handle
subsequent subcarrier channel allocation and data streaming (Figure 2). The
communication between the reader and MSMA tags includes the following threestages:■Stage 1 Inventory: During this stage, the interrogator inventory every MSMA tag andalso standard Gen2 tags with Gen2 SELECT, QUERY, and related commands. SELECT witha particular session shall be reserved for streaming start at the beginning of Stage 3 inthe current implementation. Although the algorithm of the subsequent subcarrier
allocation to each MSMA tag depends on the reader’s implementation, the collectionof received signal strength indicator (RSSI) during the inventory is usually recommended.
Our practice is to assign the weak RSSI subcarrier to subcarriers that are close topowering continuous waves [3] to reduce mutual interference caused by harmonics. In
this context, the function of subcarrier is to determine the appropriate subcarrier fromavailable subcarrier channels, whereas allocation represents actual instructions
between the reader and each tag.
■Stage 2 Subcarrier assignment and allocation: Unique subcarrier is assigned andallocated to each MSMA tag using Gen2 WRITE command to specific memory
addresses.
A special frame structure is introduced and explained in the subsequent section toallocate and calibrate the subcarrier frequency produced by an MSMA tag. Our
implementation of subcarrier allocation is described in [4]. After the subcarrier
allocation, the slave sensor is configured through an SPI. The SPI communication is
encapsulated in Gen2 WRITE command.
■Stage 3 Streaming: To start streaming from all MSMA tags, the reader sends a SELECT
command of Gen2 with session S3 in the current implemenation. The implementation
determines how to continuously retrieve data from the sensor through an SPI.

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Streaming extension of Gen2 communication protocol

Interrogator
stage1:

Sensor tag
Inventory

iterate for each tag
subcarrier assignment
stage2:
sensor configuration

stream start
stage3:streaming

stream stop

not specified in thisversion of specification

Figure 2 Communication prototype between interrogator and sensor tag. Shaded blocks represent anadditional protocol on top of Gen2

2 Communication protocol and sensor control
2.1 Subcarrier frequency and symbol definition
In Stage 3 of communication, one symbol of chip or bit shall be represented with at least
two cycles of subcarrier. If a symbol is represented with one cycle of subcarrier, it isbaseband coding. The subcarrier frequencies in MSMA comprise integer multiples of basesubcarrier frequency (Figure 3). In the figure, three base subcarrier frequencies are denotedby subcarrier 1 with ms = 1, 2, 3. Notably, this coding is only applied to Stage 3; thestandardized Gen2 coding and modulation specified by the reader can be employed inStages 1 and 2.

For example, when the symbol rate in the streaming phase is 5 kbps and ms = 2 and nocoding is introduced; the frequencies of subcarrier 1, 2, and 3 are 10, 20, and 30 kHz,
respectively. When symbol rate is 5 kbps and ms = 3, the frequencies are 15, 30, and 45 kHz,

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Streaming extension of Gen2 communication protocol

respectively. Similarly, the arbitrary bitrate of multiple subcarriers can be realized byadjusting the subcarrier frequency and coding rules.

To facilitate the demodulation in the reader for consecutive zeros or ones, we employ theMiller encoding on top of subcarrier coding in this specification 1.

ms=2

one symbol duration

ms=3

ms=4

subcarrier3

subcarrier 2

subcarrier 1Time
one subcarrier cycle
Figure 3 Subcarrier frequency and symbol

The state diagram of Miller encoding is shown in Figure 4.

Convolution coding will be used in the next edition of this extension protocol, which will be
disclosed in 2022.

1

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Streaming extension of Gen2 communication protocol

0/00Internal state

1/10
1/01

1/01

00

Input/Output

10

0/00
0/11

11

1/10

01

0/11

Figure 4 Miller encoding state transition

The subcarrier is XORed with Miller encoded baseband signal, except for the preamble as
explained below.

2.2 Streaming frame
An MSMA tag composes a continuous frame (Figure 5) to transfer streaming data to thereader in Stage 3 of the protocol. The leading 5 bits are the preamble without Miller
encoding. The rest of the frame shall be encoded with the Miller coding. The CRC-5 2 isgenerated by convoluting the frame starting from the first bit of zone with the characteristic
equation of x5+x3+1, Preset b01001. If there is no error in the return link, by applying the samegeneration polynomial until the end of CRC-5, the residue shall be b00000. This CRC-5
generation is the same as Gen2.
Zone ID is specified by the reader. Sequence ID is the frame ID automatically incremented
by one in each frame. The data length N is specified by the reader with STR_CNT register.
Preamble

Zone ID

Sequence ID

Data

CRC5

5 bit

3 bits8 bit (0-255 sequential data)

N×8 bits

5 bits001

255

equivalent
1010101010

Figure 5 Return link frame structure in the streaming mode2

CRC-16 will be used in the next version of protocol for strong error detection.

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Streaming extension of Gen2 communication protocol

2.3 Writing configuration with Gen2 WRITE command
The reader allocates subcarriers to tags and configures sensors using Gen2 WRITE
command. The structure of a WRITE command is shown in Figure 6. WordPtr uses Extensible
Bit Vectors defined in Gen2. Special register addresses for subcarrier allocation and sensor
configuration will be specified.
Write (8bit)

Membank

WordPtr

Data ( XORed withHandle CRC16

handle)11000011

2 bits(EBV)

16 bits(11:user)
Figure 6 Gen2 WRITE command

The response from a tag to the reader after receiving a WRITE command is as follows: Upon
receiving the WRITE command, a tag responds with the following delayed reply. When an
MSMA tag fails to perform the instructed write or configure, it shall reply with Success/Fail = 1
with a proper error code defined in Annex I of [1].

Preamble

HeaderHandle/Error code

CRC16

10 bits

1 bit

16 bits

16 bits

4M/BLF + 010111

0: successhandle4M/BLF + 010111

1: failError code

The special user memory addresses to MSMA tag configurations are defined in Table 1.

Table 1 Memory assignment

Memory alias

Description

Memory WordPtr

SPI_WRITE

Write one byte data to SPI

80 H

DCO_CNT

Set subcarrier frequency

81 H

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Streaming extension of Gen2 communication protocol

Set the division number of the

SUB_DIV

82 H

tag clock and the bit rate of
the subcarrier
Set the WRITE and READ

SPI_INST

83 H

instruction word used in SPI
Specify the leading address

STR_CNT

84 H

and the number of bytes of thesensor to read. Zone ID can also
be specified with thiscommand

The register’s address in the user memory bank and the word format to be written are
defined as follows. The value shall be stored as MSB first byte order 3.
SPI _WRITE (80 H)
The high byte is the address, and the low byte is the data point to be written. The tag uses
a sensor-specific WRITE command specified in the SPI_INST register. (0×0A for ADXL362).
15

14

13

12

11

10

9

8

7

Address

6

5

4

3

2

1

0

Data

DCO_CNT (81 H)
15

14

13

12

11

10

9

8

7

6

5

4

3

2

1

0

X

X

C3

C2

C1

C0

M4 M3 M2 M1 M0 F4

F3

F2

F1

F0

10

9

2

1

0

SUB_DIV (82 H)
15 14 13 12

3

11

8

7

6

5

4

3

Original intention was LSB first. This may change in the next edition.

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Streaming extension of Gen2 communication protocol

X

X

X

X

X

X

S2

S1

S0

B6

B5

B4

B3 B2 B1 B0

S2，S1，and S0：Subcarrier divider control words;
bit rate：B0–B6: bit rate divider control words

SPI_INST (83 H)
This word defines the WRITE and READ command code. High 8 bits for WRITE and low 8 bitsfor READ sensor and RFIC communication are shown in Figure 7; for ADXL362, they are 0×0A
and 0×0B, respectively.
15

14

13

12

11

10

9

8

7

0×0A

6

5

4

3

2

1

0

0×0B

STR_CNT (84 H)
This word defines the data point to be read from a sensor. The high 8 bits (15:8) is the starting
address. Bit 7–4 is the number of bytes to be read, Bit 3 is to select antenna, and Bit 2 is the 0Zone ID. For ADXL362 to read XDATA, YDATA, ZDATA, TEMP (total 16 × 4 = 64 bits = 8 bytes),
the register values are as follows:
15

14

13

Address

12

11

10

9

8

7

6

5

# of bytes to

4

3

2

1

RFU

ZONE ID

0

001

0

read
0×08

1000

2.4 Subcarrier allocation and bit rate configuration
Although the design is required to generate subcarrier frequency in an MSMA tag, therecommended way to deliver specified subcarrier frequency with a relatively slow clock
rate of the master clock in RFIC is by adjusting the frequency of the oscillator in a tag to be
an integer multiple of designated subcarrier frequency. Alternatively, subcarrier frequency
can be produced by decimating a single master clock. However, in such a design, a highJuly 7, 2021

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Streaming extension of Gen2 communication protocol

subcarrier frequency tends to involve bias, which may violate the subcarrier accuracy
requirement.

Because the subcarrier frequency produced by an MSMA tag does not immediately matchthe specified frequency owing to the instability of the DCO clock, this communication
protocol can perform an iterative adjustment (Figure 1). The first SUB_DIV to specify thesubcarrier frequency division allows using the iterative adjustment to specify the masterclock of an MSMA tag.
Interrogator

MSMA tag

specify the decimation numberof subcarrier frequency N (SUB_DIV)
delayed reply

specify the N times ofsubcarrier frequency with 14 bits value (DCO_CNT)
subcarrier frequency
produced for 8 msec
delayed reply
measurement
adjust DCO_CNT value

specify the N times ofsubcarrier frequency with 14 bits value (DCO_CNT)

Figure 7 Iterative subcarrier frequency adjustment

The 14-bits DCO value comprises overlapped coarse, middle, and find registers (Figure 8).

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Streaming extension of Gen2 communication protocolcoarsemiddlefine

Figure 8 Overlapped DCO_CNT register value

The 14-bit values X relates to the actual frequency as follows:
𝑓𝑓 = 400 𝑋𝑋 + 691200

Consequently, one subcarrier frequency can be represented in general with four patterns ofregister values, allowing some errors in the adjusting accuracy of DCO (Figure 9).

overlap bit = 1
x2

x1

x1

x2

1
0

x2

overlap bit = 0

y-1

y-2

0
1

y-1

y-2

x1

carry down
x2

x1

0
0

y-1

y-2

y-1

y-2

1
1

Figure 9 Candidates to represents one overlap bit

However, the increase in the subcarrier frequency against a unit increase in each registervalue cannot exceed 2.0 because there will be a gap subcarrier frequency that cannot becompensated in such cases (Figure 10).

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Streaming extension of Gen2 communication protocol

Subcarrier frequency

coarsecoarse value
n-1

middlenn+1Figure 10 Slopes of each DCO value cannot be different more than two times. This figure is depicted
for coarse and middle registers.

The subcarrier and bit rate is illustrated in Table 2.

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Streaming extension of Gen2 communication protocol

Table 2 Subcarrier and bitrate allocation
DCO Clock
dividing ratio(MHz)

Code (14bits)
C
0100
0111
1010
0011
0100
0110
0111
1001
1010
0010
0011
0011
0100
0101
0110
0111
0111
1000
1001
1010
1010
1011
0010
0010
0011
0011
0011
0100
0100
0101
0101
0101
0110
0110
0111
0111
0111
1000
1000
1000
1001
1001
1010
1010
1010
1011
1011
0010
0010
0010
0010
0010
0011
0011
0011
0011
0011
0100
0100

M

F

11011
11101
11111
10010
11011
10100
11101
10110
11111
10101
10010
11110
11011
10111
10100
10000
11101
11001
10110
10010
11111
11011
10101
11011
10010
11000
11110
10100
11011
10001
10111
11101
10100
11010
10000
10110
11101
10011
11001
11111
10110
11100
10010
11000
11111
10101
11011
10010
10101
11000
11011
11110
10010
10101
11000
11011
11110
10001
10100

10000
10000
10000
10000
10000
10000
10000
10000
10000
11000
10000
11000
10000
11000
10000
11000
10000
11000
10000
11000
10000
11000
11000
11100
10000
10100
11000
11100
10000
10100
11000
11100
10000
10100
11000
11100
10000
10100
11000
11100
10000
10100
11000
11100
10000
10100
11000
10110
11000
11010
11100
11110
10000
10010
10100
10110
11000
11010
11100

1.28
1.6
1.92
1.12
1.28
1.44
1.6
1.76
1.92
1.04
1.12
1.2
1.28
1.36
1.44
1.52
1.6
1.68
1.76
1.84
1.92
2
1.04
1.08
1.12
1.16
1.2
1.24
1.28
1.32
1.36
1.4
1.44
1.48
1.52
1.56
1.6
1.64
1.68
1.72
1.76
1.8
1.84
1.88
1.92
1.96
2
1.02
1.04
1.06
1.08
1.1
1.12
1.14
1.16
1.18
1.2
1.22
1.24

Dividing ratio sub. Freq
(3 bits)
(kHz)
32
32
32
16
16
16
16
16
16
8
8
8
8
8
8
8
8
8
8
8
8
8
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
2
2
2
2
2
2
2
2
2
2
2
2

101
101
101
100
100
100
100
100
100
011
011
011
011
011
011
011
011
011
011
011
011
011
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
010
001
001
001
001
001
001
001
001
001
001
001
001

100kbps

40
50
60
70
80
90
100
110
120
130
140
150
160
170
180
190
200 0000001
210
220
230
240
250
260
270
280
290
300
310
320
330
340
350
360
370
380
390
400 0000010
410
420
430
440
450
460
470
480
490
500
510
520
530
540
550
560
570
580
590
600 0000011
610
620

40kbps20kbps

10kbps5kbps

0000001

00000100000100
0000101
000011000001110001000
0001001
000101000010110001100
0001101
000111000011110010000
0010001
001001000100110010100
0010101
001011000101110011000
0011001
001101000110110011100
0011101
001111000111110100000
0100001
010001001000110100100
0100101
010011001001110101000
0101001
010101001010110101100
0101101
010111001011110110000
0110001011001001100110110100
0110101
011011001101110111000
0111001
011101001110110111100
0111101
011111000000110000001

00000100000100
0000101

00000110000110000011100000100000100

0001000
0001001

0000101

00010100001011000001100001100001100
0001101

0000111000111000011110000100

0001000

0010000
0010001

0001001

001001000100110000101

00010100010100
0010100

00010110010110001011100001100001100

0011000
0011001

0001101

00110100011011000011100011100011100
0011101

000111100111100011111

A concrete example of subcarrier frequency allocation is explained below.

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Streaming extension of Gen2 communication protocoli.

The reader writes to SUB_DIV register as 4 division = b100. The bit rate value inthe word does not matter in this particular SUB_DIV.

ii.

The interrogator writes to DCO_CNT register with an appropriate frequency
value.

iii.

The tag replies with the DCO_CNT divided by four subcarrier frequencies for
8 ms.

iv.

The reader samples the information regarding 1/4 DCO frequency and issues
an updated DCO_CNT value to compensate for the error.

Example:Assuming an interrogator wants to allocate a 200-kHz subcarrier to an MSMA tag after theinventory, the DCO frequency of the MSMA tag should be 1.6 MHz according to Table 2. For
DCO control, the interrogator expects to receive a 400 kHz (1/4 DCO) subcarrier for 8 ms
after issuing a DCO_CTL.
i.

DCO_CTL is 0111 11101 10000. Suppose that the received subcarrier is404000 Hz, which is approximately 1% higher than the designated frequency.
Interrogator needs to lower the tag’s clock by approximately 1%.

ii.

The interrogator knows the DCO frequency is 1.6 MHz and the received
subcarrier frequency is multiplied by four, yielding 1616 = 404 × 4 kHz, whichis 16 kHz higher than the designated frequency. The DCO frequency can be
adjusted with 0.4-kHz resolution for 1 bit of DCO fine division (5 bits from LSB).

iii.

The bias 16 kHz can be compensated with 16/0.4 = 40 = 0 × 28 = b0010 1000,
which is subtracted from the original DCO_CNL = 0111 11101 10000, yielding
0111 11100 01000.

2.5 Sensor configuration
Depending on the sensor type, sensor configuration is needed through SPI by writing to
SPI_WRITE register. Example configuration for Analog device ADXL362 is illustrated in Annex
A.

2.6 Sensor data streaming SPI interface exchange
An MSMA chip will collect sensor data through SPI, and plug the data into the streaming
frame. Data is collected by providing the SPI clock synchronizing to the radio interface

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Streaming extension of Gen2 communication protocol

bitrate. Consequently, the buffer between SPI and the backscatter baseband can be
minimized.
CS

MOSI

Instruction 1B

Address 1B

Instruction 1B

Address 1B

DATA Nx16

MISO

backscatter link

Preamble 5

Zone 3SEQ 8DATA Nx16

DATA Nx16

CRC-5

Preamble 5

Zone 3SEQ 8DATA Nx16

CRC-5

Figure 11 Sensor data encapsulation in the streaming stage

2.7 Start streaming
Start streaming is implemented using a special SELECT command (Session S3 is used as thetarget of the SELECT command) because SELECT is processed by all tags in the view field
without producing any response 4.
Select the Zone ID by SELECT command specifying the user memory address 1 to obtain thefollowing:
SelectTargetActionMembank

Pointer

Length

Mask

Truncate

CRC

4

3

3

2

EBV

8

Variable

1

16

1010

011

000-101 11(User)

0000

0000

Zone ID 0

0000

0011

CRC-1
6

Figure 13 Selecting target tags before streaming

Notably, SELECT can only be applicable to EEPROM (00H-07H).

In the next edition of this extension, An RFU command will be used for start and stop
streaming.

4

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Streaming extension of Gen2 communication protocol

2.8 Stream stop
To stop streaming, we just stop providing CW from the interrogator. Further control will beconsidered in the next edition of this extension.

3 Reference[1]. “ISO/IEC 18000-63, Information Technology–Radio frequency identification for item
management-, Part 63 parameters for air interface communications at 860 MHz to960 MHz type C,” 2015.
[2]. J. Mitsugi, Y. Kawakita, K. Egawa, and H. Ichikawa, "Perfectly synchronizedStreaming from multiple digitally modulated backscatter sensor tags,” IEEE Journalof Radio Frequency Identification, vol. 3, no. 3, pp. 149-156, Sept. 2019, doi:
10.1109/JRFID.2019.2914246.
[3]. Nitish Rajoria, Yuki Igarashi, Jin Mitsugi, Yusuke Kawakita, and Haruhisa Ichikawa,“Comparative analysis on channel allocation schemes in multiple subcarrier passive
communication system,” IEICE TRANSACTIONS on Communications Vol.E98-B No.9
pp.1777-1784, (2015). DOI: 10.1587/transcom.E98.B.1777.
[4]. Kuanfeng Tang, Chao Zhang, Maodong Wang, Xu. Shengliang, Ji. Shujiang, Na Yan,
Hao Min, and Jin Mitsugi. “A novel method to improve the subcarrier frequency
accuracy for UHF RFID sensing system,” In IEEE RFID 2021 (Virtual Event,USA). pp.1-6,(2021), doi=10.1109/RFID52461.2021.9444388.

Acknowledgement
This work includes the results of the research and development for expanding radio
resources (JPJ000254) in FY2021 of the Ministry of Internal Affairs and Communications.

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Streaming extension of Gen2 communication protocol

A. Guideline of ADXL362 configuration through Gen2 WRITE
commands
a. Prerequisite
Data streaming from ADXL362 with MSMA tag requires the following configuration using
Gen2 memory WRITE commands. The example connection between the RFIC and ADXL362
is shown in Figure 14.

MISO
MOSI
SCLK
CS

RFIC

VDD_S

SPI Slave (sensor)

VDD
VSS

PAD name

category

MISO
MOSI

SPI

SCLK

Type

Output/Input

Digital

Input

DigitalOutputDigitalOutputVSS

Signal GND

PowerInput/Output

VDD_S

SPI output voltage
regulation

Digital

Input

VDD

Power

OutputAntenna N

RF antenna N

Antenna P

RF antenna P

Valuehigh：1.6~2.5V,
low：0
high：1.6~2.5V,
low：0
high：1.6~2.5V,
low：00

1.4V~2V

Figure 14 RFIC, ADXL362, and Interrogator interface diagram

Before any GEN2 READ/WRITE command issuance, SPI READ/WRITE commands (for ADXL362,
they are 0×0B and 0×0A, respectively) shall be registered to RFIC by issuing a WRITE to
SPI_INST(83 H = EBV10000011) of user memory (bank 11) such that to obtain the following:

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Streaming extension of Gen2 communication protocol

WRITE

Membank WordPtr

Data

10000011 16 bits XOR

11000011 11

HandleCRC-16

16 bits

16 bits

with handleb. Writing to ADXL register
A Gen2 WRITE command to a specific user memory (address 0×80 = EBV 10000000) in user
memory bank (bank 11) received by the RFIC passes through to the SPI using the registered
WRITE command. For example, if we write a byte data point (0×aa) to a specific address of
ADXL (0×77), the WRITE command is as follows.
WRITE

Membank WordPtr

11000011 11

Data

HandleCRC-16

10000000 16 bits

16 bits

16 bits(0×77aa)
XOR with
HandleAfter receiving the WRITE command, tag responds with a delayed reply, which comprises a
sequence of specified subcarrier of 43-bit duration.
Preamble

Success/Fail

HandleCRC16

10 bits

1 bit

16 bits

16 bits

4M/BLF + 010111

0: success
1:Errorc. Reading from RFID memory
We can read data in RFIC memory with Gen2 READ command to obtain the following:
READ

Membank WordPtr

11000010 2 bit

EBV

WordCount Handle

CRC-16

8 bits

16 bits

16 bits

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Streaming extension of Gen2 communication protocol

Tag reply to a successful READ is as follows:
Header

MemoryHandleCRC-16

16 bits

16 bits

Words
1

Variable

For example, when we READ SPI_INST (83H) for one word, the Gen2 READ command is asfollows:
READ

Membank WordPtr

11000010 11

WordCount Handle

10000011 00000001

16 bits

CRC-16
16 bits

In the current edition of the extension, we cannot read the register value of an SPI sensor.
However, in the next edition of the extension, we enable the function.

d. Popular configuration parameters
The followings are the configuration of ADXL applied in our experiments.
Description

SPI address

Data

Note

exampleSensor activation

0×20

0×96

Data is the direct reading ofthreshold value

acceleration level that activates MEMS

setting (lower byte)

sensor. 0×96 = 150-mg activation.

Sensor activation

0×21

0×00

threshold value

The threshold level can be specified
with 11-bit data.

(higher byte)
Activity measurement

0×22

0×01

duration

To avoid false triggering, several
samples are used to distinguish
activate/inactivate. The absolute timeis determined by DATA/output data
rate (ODR). ODR is defined in Filter
Control (0×2C) register.

Activate/Inactivate

0×27

0×01

Activity Enabled = 0×01, otherwise 0×00,
activity is not detected. The sensor is

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Streaming extension of Gen2 communication protocol

controlalways on and consumes power.
Engaging inactivity by defining inactive
threshold level can be a viable option.

FIFO control

0×27

0×00

FIFO disabled. The sensor data isretrieved by RFIC and stream to theinterrogator by consecutively issuing
SPI_READ (0×0B) command by RFIC.

Filter control

0×2C

0×45

The acceleration range and ODR.
0×05 = max 2 g and 200 Hz
0×45 = max 4 g and 400 Hz

Power control

0×2D

0×00: standby (low power

0×02

consumption:10 nA)
0×02: measurement

The streaming data length and Zone ID can be configured by writing the following one
word data
15

14

13

12

11

10

9

8

Starting address

7

6

5

4

# of bytes to

3

2

1

0

RFU Zone ID

read
The address to retrieve data (12-bit data LSB) are as follows:

The example data to read XDATA, YDATA, ZDATA, TEMP (total 16 × 4 = 64 bits = 8 bytes) andZone ID = 1 is as follows.
15

14

13

12

11 10

9

8

7

6

5

4

3

2

1

0

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Streaming extension of Gen2 communication protocol

0×0E

1000

001

This 16-bit value (0×0e81) shall be written to STR_CNT (0×85) in the user memory bank with
WRITE command the such that
WRITE

Membank WordPtr

11000011 11

Data

HandleCRC-16

10000101 16 bits

16 bits

16 bits(0×0e81)
XOR
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Streaming extension of Gen2 communication protocol

B. On the SPI communication with Analog Device ADXL 362
Acceleration and temperature sensor data in ADXL362 are updated with the sampling
frequency specified in the FILTER_CNT register (0×2C) ODR bits.
Besides using FIFO, acceleration data XDATA, YDATA, ZDATA, and temperature data TEMP
can be read with Burst READ (0×0B) from the corresponding register 0×0E-0×0F, 0×10-0×11,
and 0×12-0×13, 0×14-0×15, respectively, each with 12-bit data and 4-bit padding. The
register value is updated with ODR bits such as 400 Hz = 2;5 ms at the maximum. The required
bit rate to send N consecutive samples of the specified axis data can be calculated byassuming the following backscatter frame:
Preamble

Zone

Sequence ID

Data

CRC5

4-bit

3 bits8 bits (0-255 sequential data)

N×

5 bitsequivalent

16-bits

10101010

Assuming the bit rate in the air interface to be X kbps, the maximum time to retrieve datafrom sensor through SPI is 85/X ms (Figure 15).
85/x msec (N=4)
backscatter link

Preamble 5

Zone 3SEQ 8DATA Nx16

CRC-5

Preamble 5

Zone 3SEQ 8DATA Nx16

CRC-5

Figure 15 Maximum time to collect sensor data through SPI. For 5 kbps, the maximum time is 17 ms.

Assuming N = 4, to collect XDATA, YDATA, ZDATA, and temperature yielding a total of 8
bytes, there are 85 bits to be transferred over the air interface. In SPI communications, thenumber of data that shall be collected before the data streaming demands additional two
bytes to specify the SPI reading (0×0B) and the leading address (0×0E) is shown in Figure 16.

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Streaming extension of Gen2 communication protocol

SPI bitrate > 16/17 x
CS

MOSI

MISO

Instruction 1B

Address 1B

Instruction 1B

Address 1B

DATA Nx16

DATA Nx16

Figure 16 Data transfer between RFIC and sensor through SPI

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Streaming extension of Gen2 communication protocol

C. Revision History
Date

Version

Note

June 15, 2021

1.0

Initial version

July 1, 2021

1.1

Editorial and format change

July 7, 2021

1.2

Editorial change

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23