CC2431 System-on-Chip for 2.4 GHz ZigBee®/ IEEE 802.15.4 with Location Engine Applications • • • • • • ZigBee® systems 2.4 GHz IEEE 802.15.4 systems Home/building automation Industrial Control and Monitoring Low power wireless sensor networks Access Control • • • • • • PC peripherals Set-top boxes and remote controls Consumer Electronics Container/Vehicle Tracking Active RFID Inventory Control Product Description The CC2431 is a true System-On-Chip (SOC) for wireless sensor networking ZigBee®/IEEE 802.15.4 solutions. The chip includes a location detection hardware module that can be used in so-called blind nodes (i.e. nodes with unknown location) to receive signals from nodes with known location’s. Based on this the location engine calculates an estimate of a blind node’s position. The CC2431 enables ZigBee® nodes to be built with very low total bill-of-material costs. The CC2431 combines the excellent performance of the leading CC2420 RF transceiver with an industry-standard enhanced 8051 MCU, 128 KB flash memory, 8 KB RAM and many other powerful features. Combined with the industry leading ZigBee® protocol stack (Z-Stack™) from Texas Instruments, the CC2431 provides the market’s most competitive ZigBee® solution. The CC2431 is highly suited for systems where ultra low power consumption is required. This is achieved by various operating modes. Short transition times between these modes further ensure low power consumption. Key Features • • • • • • • • • • Location Engine calculates the location of a node in a network High performance and low power 8051 microcontroller core. 2.4 GHz IEEE 802.15.4 compliant RF transceiver (industry leading CC2420 radio core). ® protocol stack (Z-Stack™) from ZigBee Texas Instruments includes support for CC2431 ‘s location engine. Excellent receiver sensitivity and robustness to interferers 128 KB in-system programmable flash 8 KB RAM, 4 KB with data retention in all power modes Powerful DMA functionality Very few external components Only a single crystal needed for mesh network systems • • • • • • • • • • Low current consumption (RX: 27 mA, TX: 27 mA, microcontroller running at 32 MHz) Only 0.5µA current consumption in powerdown mode, where external interrupts or the RTC can wake up the system 0.3 µA current consumption in power-down mode, where external interrupts can wake up the system Very fast transition times from low-power modes to active mode enables ultra low average power consumption in low duty-cycle systems CSMA/CA hardware support Wide supply voltage range (2.0 V – 3.6 V) Digital RSSI/ LQI support Battery monitor and temperature sensor ADC with up to eight inputs and configurable resolution 128-bit AES security coprocessor CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 1 of 15 CC2431 Key Features (continued) • • • • Two powerful USARTs with support for several serial protocols. Hardware debug support Watchdog timer One IEEE 802.15.4 MAC Timer, one general 16-bit timer and two 8-bit timers • • • RoHS compliant 7x7 mm QLP48 package 21 general I/O pins, two with 20 mA sink/source capability Powerful and flexible development tools available Note: The CC2431 and the CC2430 are pin compatible, and the MCU and RF parts of the CC2430-F128 are identical to the CC2431 except the Location Engine. This data sheet complements the CC2430 data sheet with a description of the Location Engine. For complete information about the CC2431, please refer to the CC2430 data sheet in addition to this data sheet. The CC2430 data sheet can be found here: http://focus.ti.com/lit/ds/symlink/cc2430.pdf CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 2 of 15 CC2431 Table Of Contents 1 REGISTER CONVENTIONS ................................................................................................................. 4 2 2.1 2.2 3 LOCATION ENGINE .............................................................................................................................. 5 LOCATION ENGINE OPERATION ................................................................................................................... 5 LOCATION ENGINE REGISTER .................................................................................................................... 10 ORDERING INFORMATION .............................................................................................................. 12 4 4.1 5 GENERAL INFORMATION ................................................................................................................ 13 DOCUMENT HISTORY ................................................................................................................................. 13 ADDRESS INFORMATION ................................................................................................................. 14 6 TI WORLDWIDE TECHNICAL SUPPORT ...................................................................................... 14 CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 3 of 15 CC2431 1 Register conventions Each RF register is described in a separate table. The table heading is given in the following format: REGISTER NAME (XDATA Address) In the register descriptions, each register bit is shown with a symbol indicating the access mode of the register bit. The register values are always given in binary notation unless prefixed by ‘0x’ which indicates hexadecimal notation. Table 1: Register bit conventions Symbol Access Mode R/W Read/write R Read only R0 Read as 0 R1 Read as 1 W Write only W0 Write as 0 W1 Write as 1 H0 Hardware clear H1 Hardware set CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 4 of 15 CC2431 2 Location Engine The Location Engine is used to estimate the position of nodes in an ad-hoc wireless network. Reference nodes exist with known coordinates, typically because they are part of an installed infrastructure. Other nodes are blind nodes, whose coordinates need to be estimated. These blind nodes are often mobile and attached to assets that need to be tracked. The Location Engine implements a distributed computation algorithm that uses received signal strength indicator (RSSI) values from known reference nodes. Performing location calculations at the node level reduces network traffic and communication delays otherwise present in a centralized computation approach. The Location Engine has the following main features: • • • • • 3 to 16 reference nodes can be used for the location estimation algorithm Location estimate with readout resolution of 0.25 meters (note: The accuracy of the location estimate will depend on several factors described below). Time to estimate node location is 50 µs to 13 ms Location range 64 x 64 meters Runs location estimation with minimum CPU usage To achieve the best possible accuracy one should use antennas that have near-isotropic radiation characteristics. The location error depends on signal environment, deployment pattern of reference nodes and the density of reference nodes in a given area. In general, having more reference nodes available improves the accuracy of the location estimation. 2.1 Location Engine Operation This section describes the basic steps required to obtain location estimates from the Location Engine. The Location Engine requires a set of three to 16 reference coordinates to be input together with a set of measured parameters. The output from the Location Engine consists of a pair of estimated location coordinates. Engine is not in use, writing a 0 to will reduce the power consumption of the CC2431 by gating off the Engine’s clock signal. LOCENG.EN Figure 1 shows the basic operation of the Location Engine. Before any input data is written, the Location Engine must be enabled by writing a 1 to the enable bit, LOCENG.EN. When the Location CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 5 of 15 CC2431 Figure 1: Location Engine Operation CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 6 of 15 CC2431 2.1.1 Reference Coordinates The Location Engine requires a set of between three and 16 reference coordinates [x0, y0, x1, y1, …, x15, y15] to be input. The reference coordinates express each reference nodes position in meters, as unsigned values in the interval [0, 63.75] meters. The finest possible readout resolution is 0.25 meter. The format used is fixed-point data with the two LSBs representing the fractional part and the remaining six bits representing the integer part, thus e.g. 63.75 is represented as 0xFF. reference coordinates are being written. Once the coordinate load process commences (LOCENG.REFLD =1), 16 coordinate pairs must always be written. However, it is possible for the Location Engine to use less than 16 reference coordinates, by marking certain reference coordinates as unused. Zeros shall be used to fill the unused reference coordinate slots, and they will be interpreted as unused when 0.0 is loaded as the RSSI value for those reference coordinates. Reference coordinates are loaded into the RF register REFCOORD. Before writing to REFCOORD, a 1 must be written to the register bit LOCENG.REFLD to indicate that a set of The reference coordinates are written in the order [x0, y0, x1, y1, …, x15, y15] to the register REFCOORD. After all coordinates have been written, a 0 is written to the register bit LOCENG.REFLD. 2.1.2 Measured Parameters After the reference coordinates have been written, a set of measured parameters must be input to the Location Engine. These parameters consist of two radio parameters: Four search boundary coordinates and 16 RSSI values. The radio parameters are the values A and n. These radio parameters are used in the Engine’s algorithm used to find the estimated location. The parameters A and n can be adjusted to describe the propagation environment in which a network of devices will operate. 2.1.2.1 Parameter Definitions The measured parameters are described in this section together with how these should be estimated. 2.1.2.1.1 Parameter A The radio parameter A is defined as the absolute value of the average power in dBm received at a close-in reference distance of one meter from the transmitter, assuming an omni-directional radiation pattern. For example, if the mean received power at one meter is -40 dBm, the parameter A is specified as 40. 2.1.2.1.2 The Engine expects the parameter A to be in the range [30.0, 50.0] with precision 0.5. The parameter A is given as an unsigned fixedpoint value where the LSB bit is the fractional bit and the remaining bits are the integer part. A typical value for A is 40.0. Parameter n The radio parameter n is defined as the path loss exponent that describes the rate at which the signal power decays with increasing distance from the transmitter. This decay is proportional to d-n where d is the distance between transmitter and receiver. As an example, in the case when the value n=2.98 is found from measurements, the closest available value of n in the lookup table is 3.00, corresponding to index 13. Therefore, the integer value 13 is used for the parameter n written to the Location Engine. The actual parameter n value written to the Location Engine is an integer index value selected from a lookup table shown in Table 2. Refer to section 2.1.2.1.3 in order to find the value for n to be used. CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 7 of 15 CC2431 Table 2: n parameter lookup table n index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 n 1.000 1.250 1.500 1.750 1.875 2.000 2.125 2.250 2.375 2.500 2.625 2.750 2.875 3.000 3.125 3.250 The parameter n is written to the Location Engine as an integer index in the range [0, 31] as the index is given as an integer value with no fractional bits, e.g. the value n = 7 is loaded n index 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 n 3.375 3.500 3.625 3.750 3.875 4.000 4.125 4.250 4.375 4.500 4.625 5.000 5.500 6.000 7.000 8.000 as 00000111. The typical value for n depends on the environment. 2.1.2.1.3 Parameter Estimation The parameters A and n can be estimated empirically by collecting RSSI data (and therefore path loss data) for which the distances between the transmitting and receiving devices are known. Figure 2 is a scatter plot of abs(RSSI) data versus log distance in meters. A least-squares best-fit line is used to glean the specific values of A and n for the environment in which the data were measured: • • A is the y-intercept of the line, and n is the slope of the line The data in Figure 2 give A=42.4 and n=2.98 for that environment. Note that the plot in this example does not show the actual y-intercept i.e. the point on the line where x=0. The value of A loaded into the engine in this case would by 42.5. The value of n loaded into the engine, is seen to be 13 from Table 2. CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 8 of 15 CC2431 Path Loss vs. log-distance for source 0x85, Z=2.1082. A=42.4103, n=2.9773 95 90 85 Path Loss (dB) 80 75 70 65 60 55 50 45 2 4 6 8 10*log10(distance) 10 12 14 Figure 2: Path loss vs. log distance 2.1.2.1.4 Search Boundary Coordinates It is possible to reduce error and estimation time by setting search boundaries for the estimated location X and Y coordinates. The maximum area that can be considered is with X and Y in the interval [0.0, 63.75] meters. where: xdelta = xmax - xmin ydelta = ymax - ymin Assume that the Location Engine search is to be limited to include only the rectangular area bounded by the coordinates [xmin, ymin] and [xmax, ymax]. Note that even when it is chosen to search in the whole possible search space, these coordinates must be entered as the coordinates for the whole space, i.e. the following values: 0.0, 63.75, 0.0, 63.75. Four search boundary parameters are entered in the following order: If some input parameters are omitted the Location Engine will not estimate correctly. xmin, xdelta , ymin, ydelta 2.1.2.1.5 RSSI Values The RSSI values are the RSSI measurements corresponding to the set of reference coordinates. The RSSI values are within the interval [-40 dBm, -95 dBm] with precision 0.5 dBm. The negative sign is removed in the value written. As an example, in the case where the value RSSI = -50.35 dB, this would be written into the location engine as 50.5. Note that a value of 0.0 must be written as RSSI value for unused reference coordinates, if less than 16 reference nodes are used. The engine will not function correctly if only some of the parameters are loaded. 2.1.2.2 Loading Parameters All measured parameters described in the previous sections are loaded into the RF register MEASPARM. Before writing to MEASPARM, a 1 must be written to the register bit LOCENG.PARLD to indicate that a set of measured parameters are being written. Once the parameter load process commences CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 9 of 15 CC2431 (LOCENG.PARLD =1), all 22 parameters must be written. The measured parameters must be written in the order [A, n, xmin, xdelta, ymin, ydelta, rssi0, rssi1, …, rssi15] to the MEASPARM register. Once the parameter load process commences 2.1.3 (LOCENG.PARLD =1) it must be completed with all 22 parameters. Included in these are the 16 RSSI values which must be all written, so any unused slots must be written as zeros. After all 22 parameters have been written, a 0 must be written to the register bit LOCENG.PARLD. Location Estimation The estimated location coordinates are given in meters in the interval [0.0, 63.75] with resolution 0.25 m. The data format uses the LSB bit as the fractional part. reading the LOCX register, to obtain the actual X value as follows: When reference coordinates and measured parameters have been loaded, the location estimate is calculated by writing 1 to the LOCENG.RUN register bit. The estimated coordinates can be read from the LOCX and LOCY registers when LOCENG.DONE is set to 1. The time until estimated coordinates can be read varies with the search boundary parameters, from 50 µs to 13 ms (with 32 MHz system clock) after LOCENG.RUN was set to 1. The Location Engine does not produce any interrupt requests. Where XLOCX is the value read from register LOCX, and xmin and xdelta are the boundary parameters used as inputs to limit the search as described in section 2.1.2.1.4. Notice that the Y coordinate read LOCY from can be used directly. X = (XLOCX - xmin +1) % ( xdelta+ 1) + xmin The estimated coordinates remain valid in the LOCX and LOCY registers until new results have been calculated or until a reset. Note that LOCENG.EN must be 1 during operation of the Location Engine. The value of the X coordinate estimate given by LOCX includes an offset value which must be removed to obtain the actual X coordinate. The offset removal must be performed after 2.2 Location Engine Register This section describes the RF registers associated with the Location Engine. These registers are: • LOCENG - Location Engine control - Reference coordinates - Measured parameters - Location estimate X - Location estimate Y and status • REFCOORD input • MEASPARM The RF registers reside in XDATA memory space. Table 3 gives an overview of register addresses while the remaining tables in this section describe each register in detail. Refer also to section 1 for Register conventions. For the remaining RF registers refer to the CC2430 Data Sheet. input • LOCX coordinate • LOCY coordinate CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 10 of 15 CC2431 Table 3 : Overview of Location Engine RF registers XDATA Address Register name Description 0xDF55 REFCOORD Reference coordinates input 0xDF56 MEASPARM Measured parameters input 0xDF57 LOCENG Location Engine control and status 0xDF58 LOCX Location estimate X coordinate 0xDF59 LOCY Location estimate Y coordinate 0xDF60 CHVER Chip Version 0xDF61 CHIPID Chip Identification REFCOORD (0xDF55) Bit Name Reset R/W Description 7:0 REFCOORD 0 R/W Location Engine reference coordinate [x0, y0, x1, y1, … x15, y15] MEASPARM (0xDF56) Bit Name Reset R/W Description 7:0 MEASPARM 0 R/W Location Engine measured parameters of channel and reference nodes [A, n, xmin, xdelta, ymin, ydelta, rssi0, rssi1, …, rssi15] LOCENG (0xDF57) Bit Name Reset R/W Description 7:5 - 00 R0 Reserved, read as 0. 4 EN 0 R/W Enable location engine 0 Disable location engine 1 Enable location engine 3 DONE 0 R Estimation completed. After 1 has been written to RUN, this bit is cleared and then set to 1 when the estimated data is ready. 2 PARLD 0 R/W Load parameters. This bit shall be written as 1 before the set of parameters are written to MEASPARM. Write 0 to this bit after the last parameter has been written. 1 REFLD 0 R/W Load reference coordinates. This bit shall be written as 1 before the set of coordinates are written to REFCOORD. Write 0 to this bit after the last coordinate has been written. 0 RUN 0 R0W1 Location estimate start. This bit shall be written as 1 when desired coordinates and parameters have been written to REFCOORD and MEASPARM registers. Estimation process starts when 1 is written to this bit. Always read as 0. LOCX (0xDF58) Bit Name Reset R/W Description 7:0 LOCX 00h R Location estimate X coordinate with offset. CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 11 of 15 CC2431 LOCY (0xDF59) Bit Name Reset R/W Description 7:0 LOCY 00h R Location estimate Y coordinate. CHVER (0xDF60) Bit Name Reset R/W Description 7:0 VERSION[7:0] 0x03 R Chip revision number. The current die revision is as follows: 0x04 : Die revision E The current number in VERSION[7:0] may not be consistent with past or future die revisions of this product CHIPID (0xDF61) Bit Name Reset R/W Description 7:0 CHIPID[7:0] 0x89 R Chip identification number. Always read as 0x89. 3 Ordering Information Table 4: Ordering Information Ordering part number Description MOQ CC2431RTC CC2431, QLP48 package, RoHS compliant Pb-free assembly, trays with 260 pcs per tray, 128 Kbytes in-system programmable flash memory, System-on-chip RF transceiver. 260 CC2431RTCR CC2431, QLP48 package, RoHS compliant Pb-free assembly, T&R with 2500 pcs per reel, 128 Kbytes in-system programmable flash memory, System-on-chip RF transceiver. 2500 CC2431ZRTC CC2431, QLP48 package, RoHS compliant Pb-free assembly, trays with 260 pcs per tray, 128 Kbytes in-system programmable flash memory, System-on-chip RF transceiver, including royalty for using TI’s ZigBee® Software Stack, Z-Stack™, in an end product 260 CC2431ZRTCR CC2431, QLP48 package, RoHS compliant Pb-free assembly, T&R with 2500 pcs per reel, 128 Kbytes in-system programmable flash memory, System-on-chip RF transceiver, including royalty for using TI’s ZigBee® Software Stack, Z-Stack™, in an end product 2500 CC2431DK CC2431 Development Kit 1 CC2431ZDK CC2431 ZigBee® Development Kit 1 CC2431EMK CC2431 Evaluation Module Kit 1 MOQ = Minimum Order Quantity T&R = tape and reel CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 12 of 15 CC2431 4 General Information 4.1 Document History Table 5: Document History Revision Date Description/Changes 2.01 2007-05-30 First data sheet for released product. Preliminary data sheets exist for engineering samples and pre-production prototype devices, but these data sheets are not complete and may be incorrect in some aspects compared with the released product. CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 13 of 15 CC2431 5 Address Information Texas Instruments Norway AS Gaustadalléen 21 N-0349 Oslo NORWAY Tel: +47 22 95 85 44 Fax: +47 22 95 85 46 Web site: http://www.ti.com/lpw 6 TI Worldwide Technical Support Internet TI Semiconductor Product Information Center Home Page: TI Semiconductor KnowledgeBase Home Page: support.ti.com support.ti.com/sc/knowledgebase Product Information Centers Americas Phone: Fax: Internet/Email: +1(972) 644-5580 +1(972) 927-6377 support.ti.com/sc/pic/americas.htm Europe, Middle East and Africa Phone: Belgium (English) Finland (English) France Germany Israel (English) Italy Netherlands (English) Russia Spain Sweden (English) United Kingdom Fax: Internet: +32 (0) 27 45 54 32 +358 (0) 9 25173948 +33 (0) 1 30 70 11 64 +49 (0) 8161 80 33 11 180 949 0107 800 79 11 37 +31 (0) 546 87 95 45 +7 (0) 95 363 4824 +34 902 35 40 28 +46 (0) 8587 555 22 +44 (0) 1604 66 33 99 +49 (0) 8161 80 2045 support.ti.com/sc/pic/euro.htm Japan Fax Internet/Email International Domestic International Domestic +81-3-3344-5317 0120-81-0036 support.ti.com/sc/pic/japan.htm www.tij.co.jp/pic CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 14 of 15 CC2431 Asia Phone Fax Email Internet International Domestic Australia China Hong Kong India Indonesia Korea Malaysia New Zealand Philippines Singapore Taiwan Thailand +886-2-23786800 Toll-Free Number 1-800-999-084 800-820-8682 800-96-5941 +91-80-51381665 (Toll) 001-803-8861-1006 080-551-2804 1-800-80-3973 0800-446-934 1-800-765-7404 800-886-1028 0800-006800 001-800-886-0010 +886-2-2378-6808 [email protected] or [email protected] support.ti.com/sc/pic/asia.htm CC2431 Data Sheet (Rev. 2.01) SWRS034B Page 15 of 15 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of TI information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Information of third parties may be subject to additional restrictions. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. TI products are not authorized for use in safety-critical applications (such as life support) where a failure of the TI product would reasonably be expected to cause severe personal injury or death, unless officers of the parties have executed an agreement specifically governing such use. Buyers represent that they have all necessary expertise in the safety and regulatory ramifications of their applications, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of TI products in such safety-critical applications, notwithstanding any applications-related information or support that may be provided by TI. Further, Buyers must fully indemnify TI and its representatives against any damages arising out of the use of TI products in such safety-critical applications. TI products are neither designed nor intended for use in military/aerospace applications or environments unless the TI products are specifically designated by TI as military-grade or "enhanced plastic." Only products designated by TI as military-grade meet military specifications. Buyers acknowledge and agree that any such use of TI products which TI has not designated as military-grade is solely at the Buyer's risk, and that they are solely responsible for compliance with all legal and regulatory requirements in connection with such use. TI products are neither designed nor intended for use in automotive applications or environments unless the specific TI products are designated by TI as compliant with ISO/TS 16949 requirements. Buyers acknowledge and agree that, if they use any non-designated products in automotive applications, TI will not be responsible for any failure to meet such requirements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions: Products Applications Amplifiers amplifier.ti.com Audio www.ti.com/audio Data Converters dataconverter.ti.com Automotive www.ti.com/automotive DSP dsp.ti.com Broadband www.ti.com/broadband Interface interface.ti.com Digital Control www.ti.com/digitalcontrol Logic logic.ti.com Military www.ti.com/military Power Mgmt power.ti.com Optical Networking www.ti.com/opticalnetwork Microcontrollers microcontroller.ti.com Security www.ti.com/security RFID www.ti-rfid.com Telephony www.ti.com/telephony Low Power Wireless www.ti.com/lpw Video & Imaging www.ti.com/video Wireless www.ti.com/wireless Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265 Copyright © 2007, Texas Instruments Incorporated