白皮書：Stellaris? LM4F 系列微控制器(zslcn周生烈編譯摘注)

zslcn周生烈 2011-10-18

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白皮書：Stellaris? LM4F 系列微控制器(zslcn周生烈編譯摘注)

DSP,MAC,SIMD,API,乘法部件，除法部件,，浮點指令

Miguel Morales

Director of Marketing Stellaris Microcontrollers Texas Instruments

Introduction 簡介

Stellaris? microcontrollers (MCUs) were the first MCU on the market to be based on the ARM? Cortex-M core, an architecture that has quickly become a top choice for many developers across the globe. Since its establishment, the Stellaris product line has remained true to its original goals – providing the broadest portfolio of highly connected, low cost and easy-to-use 32-bit microcontrollers. The latest Stellaris LM4F series refines the offering of MCUs, greatly improving performance and raising features to a new level of quality.

Stellaris?微控制器（MCU）是市場上基于ARM? Cortex- M內(nèi)核的第一個MCU,；這種架構(gòu)已迅速成為世界各地許多開發(fā)商的首選架構(gòu)。自從這種架構(gòu)構(gòu)成以來,Stellaris產(chǎn)品系列一直遵循著其既定的目標--保證所提供的32位微控制器,具有高度的可連接性,、適應范圍又最為廣泛的組合包,，而且成本低，易于使用,。最新的Stellaris LM4F系列更是優(yōu)化了所提供的MCU,，極大地改善了性能,提升了功能，使系列產(chǎn)品提高到一個新的質(zhì)量水平,。

An Introduction to the Stellaris? LM4F Family of Microcontrollers

Leading analog integration, best-in-class low-power consumption and floating-point performance in next generation Stellaris ARM? Cortex-M microcontrollers

第二代Stellaris ARM?的Cortex- M的微控制器,具有領先的模擬集成,、最好一流的低功耗和浮點運算性能

Stellaris LM4F microcontrollers take advantage of two significant technologies: the latest ARM Cortex-M4F core and the design techniques and process technologies perfected at Texas Instruments. The result is a 32-bit microcontroller family with processing performance that is more effective per clock cycle, integrated mixed-signal circuits that are on par with traditional standalone components, flash memory with erase-write endurance that is best-in-class and power consumption that is highly competitive with other 32-bit MCUs in both active and standby modes. Such qualities will further increase the breadth of applications powered by Stellaris MCUs and enable applications that were not previously feasible.

Stellaris LM4F微控制器吸取了兩類重要技術(shù)的技術(shù)優(yōu)勢：最新的ARM Cortex -M4F內(nèi)核,和德州儀器公司完美的設計技術(shù)及工藝技術(shù)。這就使得一個32位微控制器具有更高的處理性能,、能使每個時鐘周期更有效,、使集成的混合信號電路可以與傳統(tǒng)獨立組件的電路相比美,、有最好一流的擦寫耐久的閃存、以及在運行和待機模式的功率消耗方面與其他32位MCU相比具有高度的競爭力,。Stellaris MCU能力的這種高素質(zhì),將進一步擴大其應用范圍,使它們可以應用到以前難以勝任的應用領域中,。

The major features of Stellaris ARM Cortex-M4F microcontrollers are depicted in the block diagram of Figure 1. A more thorough list can be found in the product data sheets.

圖1的方框圖,說明了Stellaris ARM Cortex- M4F微控制器的主要特點。一個更完整的列表可以在產(chǎn)品數(shù)據(jù)表中找到,。

Fig.1-Block diagram of TI’s Stellaris LM4F series of microcontrollers.

圖1--TI的Stellaris LM4F系列微控制器方框圖

ARM Cortex-M4F: Higher performance, still compatible

ARM Cortex - M4F：性能更高,，保持兼容

The Stellaris LM4F series makes use of the most advanced ARM architecture core for microcontrollers, the Cortex-M4F. As a 32-bit architecture, Cortex-M microcontrollers enjoy a rich instruction set with far greater flexibility than 8- or even 16-bit architectures and can operate on data that is up to 32-bits wide with ease. The long and successful history of the ARM architecture in embedded applications assures the greatest selection of third-party hardware and software support, pre-packaged off-the-shelf software like stacks and real-time operating systems (RTOSs) and experienced engineering and programming personnel for any project.

Stellaris LM4F系列使用最先進的ARM體系結(jié)構(gòu) Cortex-M4F 為內(nèi)核,用于微控制器。作為一種32位的架構(gòu),，Cortex-M的微控制器,有遠比8位,、甚至16位架構(gòu)的靈活、豐富的指令集,，能方便地對直至32位的數(shù)據(jù)進行操作,。ARM架構(gòu)在嵌入式應用中長期采用和取得成功的歷史,保證了能最大程度地選取第三方硬件和軟件的支持；能取得已包裝的現(xiàn)成的軟件,如堆棧和實時操作系統(tǒng)（RTOS）,；以及對各種項目都有經(jīng)驗豐富的工程實踐和編程人員,。

Previous Stellaris generations used the original Cortex-M3 architecture. The Thumb-2 instruction set of this earlier version of the Cortex-M core is a high-density, power-efficient instruction set suitable for a wide variety of general-purpose data processing and control operations.

以前幾代的Stellaris使用最早的Cortex - M3架構(gòu)。這種Cortex - M內(nèi)核的早期版本,其Thumb-2指令集,是一種高密度的,、高效能的指令集,，適合于各種各樣的通用數(shù)據(jù)處理和控制操作。

The Cortex-M3 Thumb-2 instructions include arithmetic, logical, bit, branch and data movement operations found on many MCUs. It also adds more advanced operations and multiplication, bit-field manipulation, conditional prefixes and operates on 8-, 16- and 32-bits of data. The ARM Cortex-M3 has become a standard for modern 32-bit microcontrollers.

Cortex-M3的Thumb-2指令包括了在許多MCU中都可以找到的算術(shù),、邏輯,、位、轉(zhuǎn)移,、和數(shù)據(jù)移動操作,；它也增加了更高級的操作,以及乘法,、位-域操作,、(附加在指令前的)條件碼前綴、和在8位,、16 位,、及32位數(shù)據(jù)上的操作。ARM Cortex-M3已經(jīng)成為現(xiàn)代32位微控制器的標準,。

The new Cortex-M4 expands the instruction offering of the Cortex-M3 by adding digital signal processing (DSP) extensions and single instruction, multiple data (SIMD) instructions. The Stellaris LM4F series also includes the floating point option (the “F” in the Cortex-M4F) across the entire offering of LM4F products.

新的Cortex-M4,通過增加數(shù)字信號處理(DSP)的擴展及單指令多數(shù)據(jù)指令(SIMD),為Cortex-M3提供了擴充指令,。Stellaris LM4F系列還包括了浮點選項(在Cortex-M4F中的“F”),提供給所有LM4F產(chǎn)品。

The DSP operations of the Stellaris LM4F series include single-cycle 32-bit or dual 16-bit multiply-accumulate (MAC) instructions and saturating arithmetic instructions. Optimized SIMD instructions can perform four 8-bit or two 16-bit arithmetic operations in a single cycle and are therefore very effective at performing arithmetic operations on large arrays of data. The hardware divide logic produces a result in between 2 and 12 clock cycles. Together, these instructions add DSP-like capability to a responsive controller core.

Stellaris LM4F系列的DSP操作,包括單周期的32位或雙16位乘法累加（MAC）指令,和飽和算術(shù)指令(為了避免溢出),。優(yōu)化的SIMD指令,可以在單周期中,執(zhí)行4個8位,或兩個16位的算術(shù)運算操作,，因此在大型數(shù)組中執(zhí)行算術(shù)操作非常有效。硬件除法邏輯在2～12個時鐘周期內(nèi)產(chǎn)生結(jié)果,?？傊?，這些指令,給一個反應靈敏的控制器內(nèi)核,添加了類DSP能力。

The single precision floating-point instructions are compliant with the IEEE 754 standard and include functions such as square root and a fused MAC that enable higher precision. Numerous data type conversions

are available, speeding transitions between domains.

單精度浮點指令符合IEEE 754標準,，它包括了如平方根,、和融合的MAC等功能，使計算精度更高,。有許多可用的數(shù)據(jù)類型變換,它們加快了域間的轉(zhuǎn)換,。

Besides providing a significant performance increase for math-intensive operations, floating-point support greatly simplifies the implementation and programming of floating-point routines. It is not uncommon for a customer to spend one week developing a digital filter then spend another month converting the filter to a fixed-point implementation to ensure it is both precise and stable. This development time is not required when programmers can program their filters in the native floating-point format.

除了數(shù)學密集型操作明顯提高了性能，浮點的支持也大大簡化了浮點例程的編程和執(zhí)行,。常?？梢钥吹竭@種情況：客戶花一個星期開發(fā)一個數(shù)字濾波器,再耗費一個月的時間將濾波器變換到定點實現(xiàn),以同時保證精度和穩(wěn)定性。然而,當程序員使用器件本身的浮點格式,來編程他們的濾波器時,就不需要花費這么多開發(fā)時間了,。

Embracing Texas Instruments’integrated technologies

包含了TI的各種集成技術(shù)

Now firmly embedded into Texas Instruments’ microcontroller catalog, the new Stellaris microcontrollers have taken full advantage of the advances and technologies that TI has honed to excellence.

現(xiàn)在, 新的Stellaris微控制器,已經(jīng)把TI的久經(jīng)磨練的先進技術(shù)和工藝的全部優(yōu)點,牢牢嵌入到TI的微控制器系列產(chǎn)品中,。

In some cases, like the mixed-signal circuits and the memory structures, specific circuits were targeted. On the other hand, an aggressive process technology has led to a reduction in power consumption across the board. In the end, the Stellaris LM4F family of devices is an accumulation of many feature enhancements and technology improvements.

在某些情況下，像混合信號電路和內(nèi)存結(jié)構(gòu),，是針對特定電路的,。另一方面，挑戰(zhàn)性的工藝技術(shù),，導致了整體功耗的降低,。最后,Stellaris LM4F系列的器件,是積累了許多功能增強和技術(shù)改進成果的集中表現(xiàn)。

Precision integrated analog 精確的集成模擬電路

In building the Stellaris LM4F microcontrollers, special effort went into designing high-quality, high-resolution analog-to-digital converters (ADCs). The result is seen in the integrated high-resolution 12-bit ADC that samples as fast as 1 MSPS, a sample rate that supports both the full resolution and accuracy of the ADCs, unlike other MCUs that degrade the quality of the readings to achieve higher sample rates. Two of these

converters are on-chip and can be fed from 24 independent inputs. To enhance precision, a differential external reference voltage can be applied to dedicated inputs.

在搭建Stellaris LM4F微控制器中,，對于高質(zhì)量,、高分辨率的模擬--數(shù)字轉(zhuǎn)換器（ADC）的設計,給予了特別的重視。于是可以看到,在集成的高分辨率12位ADC中,取樣速率高達1 MSPS,，而且可以以這樣的速率支持ADC的全分辨率和全精度,；而其他MCU,則需要降低讀數(shù)的質(zhì)量來達到更高的ADC采樣率。芯片中有兩個這樣的變換器,它們可以從24個獨立的輸入端饋入模擬信號,。為了提高精度,，一個外部的差分參考電壓可以施加到專用輸入端。

The ADCs can generate processor interrupts based on a conversion completion as well as on a match to one of eight digital comparators. Readings from the ADCs can be queued, compared and averaged within the ADC. The on-chip micro direct memory access controller (μDMA) can feed ADC readings from the ADC FIFOs to RAM or another peripheral without waking up or distracting the ARM core.

ADC可以產(chǎn)生處理器中斷,；中斷基于轉(zhuǎn)換完成,并與8個數(shù)字比較器中的一個相匹配時產(chǎn)生,。來自ADC的讀數(shù)可以在ADC內(nèi)排隊、比較,、和均值,。芯片上的微型直接存儲器存取控制器（μDMA）可以將ADC的讀數(shù),從ADC的FIFO饋送到RAM,或其它外設,而不需要喚醒或打擾ARM內(nèi)核。

There are also three on-chip analog comparators that can be used with a programmable internal voltage reference detect when an input analog signal has crossed a specific threshold. These three analog comparators, along with the digital comparators, remove the requirement of continuously polling incoming ADC values and free up the CPU to focus on real-time application tasks.

還有三個片上模擬比較器,可以與一個可編程的內(nèi)部電壓參考一起,用來檢測輸入的模擬信號是否已經(jīng)越過一個特定的閾值,。這三個模擬比較器,與數(shù)字比較器一起使用,可以免除不斷輪詢ADC收入值的需要,將CPU從專注于實時應用任務中解脫出來,。

Motion control is just one application that can take advantage of fast, accurate ADCs, floating-point performance to run more sophisticated algorithms and on-chip comparators. The more quickly and precisely the motor driver can track the dynamics of a motor during actual operation, the less pushback resistance the generated PWMs will encounter and the more efficient the control signals will be. Less energy will be expended and the shaft will spin smoother and maintain speed or accelerate in spite of varying loads. The on-chip comparators can be used to check for fault conditions in the system requiring immediate response.

運動控制正是這樣的一種應用,需要發(fā)揮Stellaris LM4F快速而精確的ADC和浮點性能的優(yōu)點,結(jié)合片上比較器,以運行更復雜的算法；所形成的PWM使電機驅(qū)動器在實際運行中,能更加快速和精確地跟蹤電機的動態(tài)過程,而很少會產(chǎn)生常見的回推阻力,也使控制信號更加有效,；能在負載變動的情況下,以更少的能量代價,實現(xiàn)轉(zhuǎn)軸平穩(wěn)旋轉(zhuǎn)或加速,。片上比較器可用于檢查系統(tǒng)故障狀況,以滿足快速響應的需要,。

Reliable memory can be distinctive 與眾不同的內(nèi)存可靠性

It can be hard to get excited about memory. It is often simply taken for granted. But changing to a TI 65 nm process for the Stellaris LM4F family raises the products to a new level of reliability and integration.

通常認為,要在存儲器上取得突破,往往是很困難的。然而,用于Stellaris LM4F系列的65納米工藝,卻改變了這一狀況,將產(chǎn)品的可靠性和集成度提高到一個新水平,。

Borrowing the flash technology that TI developed for use in automotive products, the Stellaris LM4F MCUs have extended memory durability by an order of magnitude beyond competition. The minimum number of times the flash memory on these MCUs can be erased and reprogrammed is as high as 100,000 cycles. For most applications, this breakthrough eliminates any concern of wearing out the memory from re-flashing for data collection, configuration parameters or program modifications.

借鑒TI在汽車產(chǎn)品中開發(fā)的閃存技術(shù), Stellaris LM4F微控制器,以超過競爭對手一個數(shù)量級的耐久度,擴展了內(nèi)存的耐用性,。這些MCU的閃存擦除和再編程周期的次數(shù),至少在100,000次以上。對于大多數(shù)應用而言,這一突破,，使我們可以不必關(guān)心,由于對數(shù)據(jù)收集,、配置參數(shù)、或程序修改的重新刷新,而引起的存儲器的磨損,。

More of the high-reliability flash is also available for customer-written code because StellarisWare? drivers are embedded in a small mask ROM on-chip. All Stellaris LM4F MCUs have the StellarisWare binaries committed in on-chip ROM, including the peripheral drivers, the in-system programming routines, utilities such as CRC (cyclic redundancy check) algorithms, and AES (advanced encryption standard) tables. These APIs (application programming interfaces) let the programmer take full advantage of these well-proven services, routines and tables, while leaving all of the flash for customer and application-specific code.

由于StellarisWare?驅(qū)動程序嵌入在一個芯片上的掩蔽小ROM中,高可靠的閃存,對于編寫用戶代碼,就更有用處了,。所有Stellaris LM4F MCU的片上ROM,都裝上了二進制StellarisWare文件，包括外設驅(qū)動程序,、在系統(tǒng)編程例程,、以及諸如CRC（循環(huán)冗余校驗）算法和AES（高級加密標準）表等實用程序。這些API（應用編程接口）使程序員可以充分利用這些久經(jīng)考驗的服務程序,、例程,、和表格,從而用戶可以利用全部閃存來放置用戶代碼和特定的應用程序代碼。

There are many other memory features on the MCUs, but one new memory type deserves special attention. The new Stellaris LM4F MCUs have 2K bytes of secure, on-chip EEPROM. EEPROM is normally used to store long-term variables that may even need to survive power outages and dead batteries. Since the implementation is interrupt-enabled, the integrated memory allows for the execution of code while writing values to nonvolatile memory (execute-while-write). The EEPROM use is architected using a built-in wear-leveling technique that ensures each location can be modified 500,000 times. If the data was re-written 100 times a day, the EEPROM would last nearly 15 years!

在本系列MCU中的存儲器,還有許多其它的特點。有一種新的存儲器類型是值得關(guān)注的。新的Stellaris LM4F MCU有一個2K字節(jié)的片上安全EEPROM,。EEPROM通常用來保存長期變量，這在停電和電池失效的情況下常常是需要的,。由于該EEPROM執(zhí)行中斷驅(qū)動,當寫入時存儲器就會執(zhí)行代碼（寫入時執(zhí)行）。EEPROM的使用是采用內(nèi)置的磨損均衡技術(shù)構(gòu)建的,以確保每一個存儲位可以修改50萬次,。這就是說,如果每天重寫數(shù)據(jù)100次,，EEPROM的壽命能延續(xù)將近15年！

Power savings extend battery life 節(jié)電,，延長了電池壽命

The power requirements for embedded systems continue to be a key design parameter for consideration. Many end equipments run off a battery; therefore a long battery life can set a customer’s product apart from competing systems. Even mains-powered equipment often has limitations on the power budget. As an example, many new products now draw their power solely from a USB cable, which is limited by the USB specification to a maximum of 500 mA.

嵌入式系統(tǒng)的功率需求,一直是列入考慮的關(guān)鍵設計參數(shù),。許多端設備的運行不用電池，因此設計需要長壽命電池的系統(tǒng)可能把自己放在一個無法與對手的系統(tǒng)相競爭的位置,。甚至帶有電源供電的設備通常也要對供電作出限制,。作為一個例子，現(xiàn)在很多新產(chǎn)品只從USB電纜中取得電源,而USB規(guī)范限制了USB只能供給不超過500mA的電流,。

The first way TI achieved best-in-class power consumption, where class is defined by the Stellaris family of devices, was by using a proprietary 65 nanometer (nm) process. This special 65 nm process lowers power consumption for the microcontroller without sacrificing the high performance available from the ARM Cortex-M4F core. The Stellaris LM4F family is the only Cortex-M microcontroller family implemented on a process as advanced as 65nm.

TI實現(xiàn)最佳一流功耗的第一種方法,其中‘一流’是由Stellaris系列器件所定義,是使用65納米（nm）工藝專利。這個用于微控制器的特殊的65納米工藝,在不犧牲ARM Cortex-M4F內(nèi)核高性能的前提下,降低了功耗,。Stellaris LM4F系列是Cortex-M微控制器家族中唯一采用65納米先進工藝的Cortex-M MCU,。

Stellaris LM4F MCUs also have a number of clock and power domains that can be gated as needed to manage power. When the DSP or floating-point units are not needed, for example, or if any of the peripherals will be idle, power and/or clocking to those modules can be shut down in order to optimize power consumption.

Stellaris LM4F微控制器還有若干時鐘和電源域,當需要管理電源時可以控制它們。例如,在DSP或浮點單元是不需要時,或,任何外設空運行時, 這些模塊的電源與/或時鐘,都可以被關(guān)閉,以優(yōu)化功耗,。

Stellaris LM4F devices provide sleep, deep-sleep and hibernate (HIB) modes to save power when minimal functionality is required. In the hibernate mode, power to the entire chip is cut off except to the HIB block, leaving the MCU in a state where it can be brought back to life when the need arises. The HIB block includes a 32 kHz oscillator circuit, a supporting real-time clock (RTC) module, a battery monitor circuit and sixteen 32-bit words of backup battery SRAM. This minimalist implementation allows the power consumption to be reduced, in hibernate (HIB) mode, to as little as 1.6 μA. The Stellaris LM4F devices can be awakened from hibernation by an RTC match, from an external signal, or from a low voltage detection circuit.

當只需要最小功能時, Stellaris LM4F器件提供睡眠,、深度睡眠,、和休眠（HIB）模式,以節(jié)省功耗。在休眠模式下,，除了Hib塊,整個芯片的電源都被切斷,保留狀態(tài),以便在需要時恢復并從留在MCU中的狀態(tài)下啟動,。 HIB塊包括一個32 kHz振蕩器電路、一個支持實時時鐘（RTC）的模塊,，一個電池監(jiān)控電路,、和16個32位的SRAM的備用電池。這個最小的實施,允許休眠（HIB）模式的功耗減少到只有1.6μA,。Stellaris LM4F器件,可以由外部信號,通過RTC匹配來喚醒,或由低電壓檢測電路來喚醒,。

It might be minutes, hours, or even days between events that cause the device to come out of hibernation. The longer the duration and the lower the power of the hibernation state, the longer between recharges or replacement of batteries.

引起休眠被喚醒的事件間隔時間,可能是幾分鐘，幾小時,，甚至幾天,。持續(xù)時間越長,休眠狀態(tài)的功耗就越低，再次充電或更換電池的時間就更長,。

Additionally, the state of all GPIO lines can be saved during hibernation until the chip wakes up. Upon awakening, the chip goes through a power-on reset and starts executing instructions in a maximum of 500 μS. In full 80 MHz execution mode from flash, the Stellaris LM4F devices consume a typical 30 mA. A full description of the power modes is shown in Figure 2.

此外,，在休眠狀態(tài)時,所有GPIO線路狀態(tài)都能被保存,直到芯片被喚醒。在喚醒過程中,，芯片經(jīng)過一個上電復位,并在最多500微秒內(nèi)執(zhí)行指令以完成啟動過程,。在80 MHz的閃存全執(zhí)行模式中， Stellaris LM4F器件消耗通常是30 mA,。圖2全面介紹了各種電源模式,。

Fig. 2 - A full description of the power modes available on Stellaris LM4F devices

#Specs provided are nominal, running from flash, * Preliminary, subject to change

圖2 - Stellaris LM4F器件各種功率模式的全面介紹
＃所提供的規(guī)范是標稱值,自閃存中運行

*予定值,有待變更

Stellaris Cortex-M microcontrollers: The right devices for your application Stellaris Cortex-M系列微控制器：是您應用的正確選擇

With over 230 Stellaris ARM Cortex-M3 microcontrollers in production today, the Stellaris MCU portfolio provides one of the broadest offerings of ARM Cortex-M microcontrollers in the marketplace. The 40 Stellaris LM4F devices announced in 2011 are only the beginning of a much broader family of Cortex-M4F implementations.

今天已經(jīng)生產(chǎn)了超過230種Stellaris ARM Cortex-M3微控制器，投放在市場上的Stellaris MCU 組合包,是使用最廣泛的ARM Cortex-M系列微控制器中的一種,。在2011年宣布40種Stellaris LM4F器件,只是更廣泛的Cortex-M4F家族實現(xiàn)中的開始,。

A few key points from the Stellaris LM4F family have been highlighted: floating-point performance, the integrated analog, the integrated memory, and the low-power consumption. Many of these advantages come as a result of either integrating the new ARM Cortex-M4F core, leveraging the TI analog design expertise, or as a result from using TI’s differentiated 65nm process technology.

根據(jù)Stellaris LM4F系列的幾個關(guān)鍵方面,已經(jīng)強調(diào)了：浮點性能、集成的模擬電路,、集成的存儲器,、以及很低的功耗。這些優(yōu)勢中的許多都是來自于集成新的ARM Cortex-M4F內(nèi)核,、充分利用TI模擬設計方面的專業(yè)知識的結(jié)果,，或者來自于TI特有的65nm工藝技術(shù)??的結(jié)果。

For the future, customers can expect a roadmap that leads to higher integration, more performance, and even lower power. To evaluate the current LM4F devices, Texas Instruments offers the Stellaris EK-LM4F232 evaluation kit, priced at $149 USD, which includes all the hardware and software to get started in 10 minutes of less. This includes a demo of a data logging application that highlights the integrated 12-bit analog-to-digital converters (ADCs), power consumption, USB and the high-reliability flash.

對于未來,顧客可以預期的一個路線圖是,更高的集成度,、更強的性能,、和更低的功耗。為了評估當前的LM4F器件,，TI提供了Stellaris EK-LM4F232 評估套件,，售價為$ 149，其中包括所有的硬件和軟件,能在10分鐘以內(nèi)就可以啟動。套件中包含了一個數(shù)據(jù)記錄應用程序,著重在突出集成的12位A/D轉(zhuǎn)換器（ADC）,、功率消耗,、USB、和高可靠性閃存等的演示,。