1
Normally-Off MCU Architecturefor Low-power Sensor Node
Masanori Hayashikoshi (Speaker),Yohei Sato,
Hiroshi Ueki,Hiroyuki Kawai,Toru Shimizu,
Renesas Electronics Corporation
ASP-DAC 2014, Session 1S-3Jan. 21, 2014
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
2
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
3
Paradigm shift for power savings Intermittent system operation by NVRAM will be a promising
solution to low-power requirements.
4
pow
er
time
active standby
Large SRAM standby leak
SRAM based operation
pow
er
time
active standby
eFlash start-up
eFlash based operation
Data evacuation to eFlash
pow
er
time
active standby
NVRAM based operation
<Advantages>- Very low power consumption- Reliability improvement of Trs in peripheral circuits
<Features>- Fast power-on/off- No DC current during standby
Challenge for further power saving in NVRAM system application
“Normally-off computing technology” is enable to cut off the power, except for the component in work truly even in operation as a system, with synergy of NVRAM and power gating technology.
5
applicationalgorithm
scheduling
op1
op2
op3 op5
op4 op6
op7 op8
Dependence of activity
Maximize the power-off period with activity localization
(BET: Break Even Time)
If t<BET,No chance for Power-Off
op1 op5 op6 op8
op2 op3 op4 op7
activity
activity time
time
If t>BET,Chance for Power-Off
op1 op5op6op8
op2 op3 op4 op7
activity
activity time
time
PowerOff
PowerOn
Unit A
Unit B
ActivityLocalization
tBET BET
t
Technologies to realize “Normally-Off Computing”
Power-Off as long as possible, as large area as possible, if QOS is satisfied.
Power-Off during IDLE-Time of circuits, function blocks, chips, units and systems.
Application-independent Computing Platform based on Power-gating, Software-control and OS API.
6
“Normally-Off Computing” is a System-level platform technology with combining HW and SW technologies.
Power gating Non-volatile RAMDVFS, AVS, etc.Clock gating
Software TechnologyPower on-off control, OS, API
Device TechnologyCircuit Technology
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
7
Cyber-Physical System is a fundamental technology in Smart City
The advanced service can be realized with collecting real-time information in the social and natural environments.
8
Connected
Mobile
Service Vender
Internet
Sensor
Power ControlServer
Smart Grid
Network
Environmentmonitor
Power Network
BEMS, HEMSAir-conditioningmanagement,Seculity Gurd,Maintenance
Power CompanyRemote Meter Reading,Power Supply Control
Content Vender
Data CenterFinance, Government,
School,…
TelecommunicationModem
Home Security
Consumer Electronics Control
Automated Mater Reading
Motion,Thermal,Smoke Sensors
Camera
IntercomDoor Key
Living InformationService
Data Delivery with PC
Light
Power Monitoring
Gas leakDetection
Power Meter Gas MeterWater Meter
Cloud
Air Conditioning Thermal,HumiditySensor
ModemServer
Music, Visual, Game,Network service,…
Gloval Processing <Inter-net> Regional and local information
collection <Sensor-net>Therefore, sensor nodes become used extensively to gather the real-time information.
Production volume of Sensor Node Production Volume: ~10B pcs/year This volume will be much increased with the development of
cyber-physical systems.
9
PC & Server Mobile Phone & Terminal
Embedded Sensor-node
0.3Bpcs/year
1.5Bpcs/year
10Bpcs/year
(Production Volume: 2011 Data)
It becomes very important how to reduce the power consumption of huge sensor nodes.
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
10
Conventional Sensor node Sensor-modules are in “Normally-On”. Microcontroller is in “Normally-On” or “Intermittent”.
11
Network
Vcc
Microcontroller
Input
Sensor 0
Sensor n
Sensor 1
Input
Sensor modules
CPU(CPU-2)
Sensor-netInterface
DataIF
PowerControl
VddPOR
OSC
Memory
Normally-On Normally-On or Intermittent
Input
LDO
Peripheral
Sensornetwork
Challenge for Low-power Sensor nodes
12
Istby~10uA
PowerOnOverhead
TimeStandby Wakeup
50us~100ms
50ms~10s
Power
(Data communication)
Sensing
CPU processing
Power consumption change of sensor nodes
Breakdown of power consumption of sensor system
Telecom Sensor(AlwaysPower-on)
MCU(Active)MCU
(Stand-by)
11%13%
10%66%
Challenge for low-power consumption
Maximize power-off period. (MCU and Sensor is power on, when necessary)
Reduce the active current.
Power On/Off Overhead Power On and Off has Power and Time overhead. “Normally-off Computing” should manage the overhead to
reduce total-power .
13
Maximize Power-Off period- Longer Off-time, and More frequently
Minimize Power-on energy- Lower active current, and Shorter On-time
I(t)
V(t)
t
tSW-ON SW-OFFProgram
start
Power-ON
Power-ON
SW-ON SW-OFFProgramstart
Power-ON
Power-ON
Power-OFF
Power-OFF
Low-leak(OFF-time)
Low-power(ON-time)
Normally-off(Longer and
More frequently)
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
14
Normally-Off Architecture for Low-power Sensor node
Sensor-modules are in “Normally-Off”. Microcontroller is in “Normally-Off”.
15
Vcc
Microcontroller
Input
Sensor 0
Sensor n
Sensor 1
Input
Sensor modules
SensorControl(CPU-1)
(b)
CPU(CPU-2)
Sensor-netInterface
DataIF
PowerControl
VddPOR
OSC
Memory
Control Sig.
n
RTC
Vcc-1 Vcc-4
Normally-Off Power Manager(a)
Power Statement RegisterVcc-3
Sensor data buffers
(C)
Vcc-2
Normally-On
Normally-Off Normally-Off
Input
LDO
Peripheral
Network
Sensornetwork
DataIF
DataIF
Control Sig.n
HighLoad
LowLoad
(d)
Normally-Off Architecture for Low-power Sensor node (Continue)
Challenge is how to control the following key components.
Normally-Off Power Manager (a) “Power Manager” controls power on/off in all units with
data of “Power Statement Register”, and Manages task-level scheduling for activity localization.
Sensor Controller (b) Simple processing (e.g. data sampling) which was carried
out in the microcontroller, are performed in “Sensor Controller”.
Sensor Data Buffer (c) Sensor data are stored in “Sensor Data Buffer”. After that,
microcontroller performs the processing at once to reduce the number of power-on of microcontroller.
16
Normally-Off Architecture for Low-power Sensor node (Continue)
CPU in Microcontroller (d) Proposed architecture is consists of heterogeneous CPUs
with Sensor Controller(b) and CPU(d). Sensor required high load task, such as a Image sensor,
is directly processed at CPU(d). Task processed at Sensor Controller(b) and CPU(d)
respectively should be optimized with task-level scheduling method.
17
Thus, it is possible to reduce the operating frequency of the microcontroller, and to maximize the power-off time of microcontroller.
Normally-Off Power Management (1)Autonomous standby mode transition
Current microcontroller has some standby modes. “Normally-Off Power Manager” also supports the “Autonomous
standby mode transition technology” to select optimal standby mode for programmer’s usability improvement.
18
Power-OffEOHStby mode-3EOHStby mode-2EOHStby mode-1EOHIDLE EOH
ConsumptionEnergy
Task cycleBET1 BET2 BET3 BET4
ActiveEnergy
StandbyEnergy
EOH: Energy Over-HeadBET: Break Even Time
Normally-Off Power Management (2)Activity Localization technology
Sensing data is buffered in sensor data buffer, and after then, microcontroller is activated and performed the process at once.
19
It is possible to optimize the number of power on/off cycles and decrease power consumption energy.
Conventional PG control Hierarchical PG control
Td: deadline
Ti: interval
time
Stand-by
Power-on
Datasampling
Sensor MCU
Td’ := Td – Tbufeffective deadline
Ti: interval
Tbuf:buffer OH
time
Processing forN inst. bundle
Sensor MCUSensordata buff.
Power-on
Stand-by
Data sampling
Evaluation Board Evaluation board is consist of,
Sensor (Temperature, Brightness, Pyroelectric(Motion)) Microcontroller Other Peripheral circuits
20
MCU
LCD
PowerSupply
Communicationconnector
Memoryconnector
Reset SW
E1 debuggerUSB
Analogconnector
Temperature sensor
Pyroelectric(Motion)sensor
LED
RS-232C
Brightness sensor
Evaluation Results Power consumption energy is reduced by 67%.
21
0.00
1.00
2.00
3.00
4.00
5.00
6.00
- MCU: conventional PG control - Sensor: always power-on
Energy[mJ]
Reduction by 67%
- MCU: Hierarchical PG control- Sensor: Intermittent PG control
Sensor Microcontroller(MCU)
[Condition]- 3 sensors (Temp., Brightness, Pyroelectric)- Sampling cycle = 1s- Processing period = 4ms- Room temp.
Demonstration of Normally-Off Microcontroller system
Demonstrate effectiveness and adaptability of normally-off microcontroller system.
Demand transportation system with Normally-Off sensors (Pyroelectric, Camera) are under development as a demonstration with Future University Hakodate.
22
Demand transportation system based on Intelligent bus stop
Intelligent Bus Stop System with
Normally-Off.
Control Center
DirectionLocation
Dispatch depending onRequirements
Outline
Introduction Lower power requirements of sensor nodes in
smart society Challenges for low-power sensor node Proposal for normally-off architecture for low-power
sensor node Summary and Conclusions
23
Summary and Conclusion Production volume of sensor nodes is much increased with
the development of cyber-physical systems.
Normally-off architecture of microcontroller for future low-power sensor node has been proposed to reduce the power consumption of huge sensor nodes.
To realize true low-power effects with normally-off computing technology, a co-design of hardware and software technology is very important.
In this work, the power consumption energy is reduced by 67%.
Normally-Off Computing is a candidate for future low power sensor networks.
24
25
Thank you for your attention.
Top Related