This article has multiple issues. Please help improve it or discuss these issues on the talk page . (Learn how and when to remove these template messages) (Learn how and when to remove this template message)
|
The Serial Low-power Inter-chip Media Bus (SLIMbus) is a standard interface between baseband or application processors and peripheral components in mobile terminals. It was developed within the MIPI Alliance, founded by ARM, Nokia, STMicroelectronics and Texas Instruments. [1] The interface supports many digital audio components simultaneously, and carries multiple digital audio data streams at differing sample rates and bit widths.
SLIMbus is implemented as a synchronous 2-wire, configurable Time Division Multiplexed (TDM) frame structure. It has supporting bus arbitration mechanisms and message structures which permit re-configuring the bus operational characteristics to system application needs at runtime. Physically, the data line (DATA) and the clock line (CLK) interconnect multiple SLIMbus components in a multi-drop bus topology. SLIMbus devices may dynamically “drop off” the bus and “reconnect” to the bus as required by using appropriate protocols outlined in the SLIMbus specification. When used in a mobile terminal or portable product, SLIMbus may replace legacy digital audio interfaces such as PCM, I2S, [2] and SSI (Synchronous Serial Interface for digital audio), as well as some instances of many digital control buses such as I2C, [3] SPI, microWire, [4] UART, or GPIO pins on the digital audio components.
SLIMbus Device Class definitions are those which specify the minimum requirements for Device control data, Device behavior, and data Transport Protocol support. There are four SLIMbus Device Classes defined at the release of Version 1.01 of the SLIMbus specification: Manager, Framer, Interface, and Generic. Complete SLIMbus systems can be implemented without any additional Device Classes.
The Manager Device is responsible for configuring SLIMbus, and performs bus administration (administration of Components and Devices, bus configuration, and dynamic channel allocation) and is typically located in a baseband or application processor rather than in a peripheral component.
The Framer delivers a clock signal on the CLK line to all SLIMbus Components, and also contains logic to transmit the Frame Sync and Framing Information channels on the DATA line.
The Interface Device provides bus management services, monitors the Physical Layer for errors, reports information about the status of a SLIMbus Component, and otherwise manages the Component such that the Devices within it will function properly on the bus.
To implement a functional SLIMbus component always requires the use of a SLIMbus Interface Device, plus the function to be performed, such as DAC, ADC, digital amplifier, and so on.
A Generic Device is a Device other than a Manager, Framer, or Interface. A Generic Device is generally considered to be the device to provide certain application functionality, for example, conversion from digital audio to analog (DAC) and vice versa (ADC).
A SLIMbus Component contains two or more SLIMbus Devices. A SLIMbus Component will have only one SLIMbus Interface Device (INTERFACE), and may have one or more other types of SLIMbus devices which perform a particular function (FUNCTION).
A SLIMbus Port (P) provides the connection path for data flow between Devices. SLIMbus Ports are normally used for digital audio data flow, but may also be used for other digital data flow.
Port capabilities vary depending upon the Device and are to be specified in the Component data sheet. Typical Port attributes include data direction, i.e. input-only (sink), output-only (source) or both input and output, supported Transport Protocols, and data width.
A simple SLIMbus Component example is shown in Figure 1 below, and a complex SLIMbus Component example is shown in Figure 2 below.
All SLIMbus Devices use DATA and CLK to synchronize with the bus configuration in use, to receive or transmit messages and data, and to implement bus arbitration, collision detection, and contention resolution between devices.
For all SLIMbus Components (except one containing a Framer Device), the CLK terminal is input only. If a SLIMbus Component is the Framer Device, or contains a Framer Device, the CLK signal is bi-directional.
For all SLIMbus Components, the DATA line is bidirectional, and carries all information sent or received on the bus using Non-Return-to-Zero Inverted (NRZI) encoding.
The DATA line is driven on the positive edge and read on the negative edge of the CLK line. The DATA line can be driven high, driven low, or held at the high or low level by an internal bus-holder circuit, depending upon the particular operational mode of a SLIMbus Device.
The SLIMbus interface DATA and CLK lines use CMOS-like single-ended, ground referenced, rail-to-rail, voltage mode signals, and signaling voltages are specified with respect to the interface supply voltage (+1.8Vdd or +1.2Vdd are permitted). For EMI performance reasons, slew rate limits have been specified for SLIMbus.
The SLIMbus CLK line frequency is determined by a range of "Root" clock frequencies up to 28 MHz, and 10 Clock Gears for altering the clock frequency by powers of 2 over a span of 512x from lowest to highest Gear. The Root Frequency is defined as 2(10-G) times the frequency of the CLK line. For G=10, the CLK line frequency and Root Frequency are equal.
The SLIMbus CLK may also be stopped and restarted.
SLIMbus CLK frequencies and data transport protocols will support all common digital audio converter over-sampling frequencies and associated sample rates.
The SLIMbus Frame Structure has five building blocks: Cells, Slots, Frames, Subframes, and Superframes.
A Cell is defined as a region of the DATA signal that is bounded by two consecutive positive edges of the CLK line and holds a single bit of information.
A Slot is defined as four contiguous Cells (4-bits transmitted in MSB to LSB order). Bandwidth allocation for various data organizations, from 4-bits to 32-bits or more, can be done by grouping 4-bit Slots.
A Frame is defined as 192 (0 through 191) contiguous Slots and are transmitted as S0, followed by S1, S2 ... S191 in that order. The first Slot (Slot 0) of each Frame is a Control Space slot which contains the four (4) bit Frame Sync symbol. Slot S96 of each Frame is also a Control Space slot which contains four (4) bits of Framing Information.
The active Framer writes all Framing Information to the Data line at the appropriate time.
A Subframe is defined as the division of the Frame Structure at which Control Space and Data Space are interleaved. A Subframe is partitioned into 1 or more slots of Control Space, followed by 0 or more slots of Data Space.
As shown in Figure 4 below, the Subframe length is programmable to 6, 8, 24 or 32 contiguous Slots (24, 32, 96 or 128 Cells). The number of possible Subframes per Frame is therefore 32, 24, 8, or 6 respectively. The Subframe configuration used can be dynamically changed depending upon the data flow requirements of the applications being supported at the time.
4 of the Control space slots are reserved for a frame sync symbol, 4 bits if a Framing Information word, and 8 bits of Guide Byte. The remainder is available for more general control messages.
Any Slots not allocated to Control Space are considered Data Space.
A Superframe is defined as eight contiguous Frames (1536 Slots). Frames within a Superframe are labeled Frame 0 through Frame 7.
The duration of a Superframe is fixed in terms of Slots (and, therefore, Cells), but not in terms of time. The Superframe rate can be dynamically changed on SLIMbus to suit the particular application by changing either SLIMbus Root Frequency or Clock Gear, or both.
Information on the SLIMbus DATA line is allocated to Control Space and Data Space channels.
The Control Space carries bus configuration and synchronization information as well as inter-Device Message communication. The Control Space may be dynamically programmed to take as much of the SLIMbus bandwidth as required, even up to 100% at times.
Data Space, when present, carries application-specific information such as isochronous and asynchronous data streams.
SLIMbus Components convey control and data information between each other using Control and Data Channels with Transport Protocols to achieve the required system operation. Messages are used for Control functions.
Channels can be established between a pair of Devices (inter-Device communication), or between one Device and many Devices (broadcast communication), or in the case of the Message Channel, from all devices to all other devices (shared).
Control Space is divided into three types of channels: Framing, Guide, and Message.
The Framing Channel occupies Slots 0 and 96 of each Frame. (Since all Subframe lengths divide 96, these Slots are always available for the purpose.) Slot 0 holds a fixed Frame Sync symbol (10112), while Slot 96 holds 4 bits of a Framing Information word. Over the course of a Superframe, 32 bits of Framing Information are available. Some of these hold a fixed bit pattern used to acquire Superframe synchronization (0x011xxx2), while the others hold other critical configuration information.
The Guide Channel consists of the first 2 non-Framing control Slots in each Superframe. This "guide byte" is normally 0, but if a control message straddles a Superframe boundary, it indicates the number of bytes until the end of that message.
The Message Channel consists of all remaining Slots. It carries various types of information including bus configuration announcements, Device control and Device status.
The format of Control Space is determined by a 5-bit Subframe mode identifier transmitted in the Framing Information word. This communicates the Subframe length and the number of control Slots. The number of control Slots is limited to the choices of 1, 2, 3, 4, 6, 8, 12, 16, or 24. Adding the limitations that the number of control Slots must be less than the Subframe length produces 26 valid combinations. A special encoding for "100% Control Space", in which case the Subframe length is unimportant, produces 27 valid modes. (Modes 1–3, 20 and 30 are not valid.)
Data Channels are one or more contiguous Data Slots (Segments) and are dynamically created by the active Manager depending on the application and size of Data Space available. A Data Channel, and therefore the structure of a Segment, is defined by parameters such as Data rate, type, field length, and required Transport Protocol.
Segments repeat at known intervals and behave as virtual bus's with their own bandwidth guarantee and latency.
A Segment, shown below in Figure 5, has TAG (2 Slots), AUX (2 Slots), and DATA fields. The TAG and AUX fields are optional. If used, the TAG bits carry flow control information for the data channel, while the auxiliary (AUX) bits carry side information relating to the content of the DATA field. The data payload may or may not fill the entire allotted DATA field.
A Data Channel has exactly one data source at a time and may have one or more data sinks depending upon the Transport Protocol used in the channel.
Flow Control in the Channel, if needed, depends on the Devices and the type of Data involved. TAG bits are used to carry the flow control information.
SLIMbus Device Ports are associated with Data Channels using appropriate channel connection and dis-connection Messages. For data flow between Ports attached to Channels, SLIMbus supports a small group of frequently used Transport Protocols (including a User Defined Transport Protocol) which define data flow type, flow control mechanism, and a side-channel (if any) for any additional application-specific information. A summary of the Transport Protocols is shown in Table 1.
TP | Protocol Name | Type | # of TAG field Slots |
---|---|---|---|
0 | Isochronous | Multicast | 0 |
1 | Pushed | Multicast | 1 |
2 | Pulled | Unicast | 1 |
3 | Locked | Multicast | 0 |
4 | Asynchronous – Simplex | Unicast | 1 |
5 | Asynchronous – Half-duplex | Unicast | 1 |
6 | Extended Asynchronous – Simplex | Unicast | 2 |
7 | Extended Asynchronous – Half duplex | Unicast | 2 |
8 to 13 | Reserved | - | - |
14 | User Defined 1 | - | 1 |
15 | User Defined 2 | - | 2 |
User 1 & 2 protocols are used to extend SLIMbus's data transmission mechanisms and it is assumed that a Device connected to a User Protocol Data Channel knows the definition of the TAG and AUX bits and how they are used.
A SLIMbus system for illustrative purposes only is shown in Figure 7 below. All of the Components are different from each other. Note that the upper left SLIMbus Component in this example contains a Framer Device (F), and therefore the CLK signal for this component is bidirectional.
The upper left SLIMbus Component also contains a Manager Device (M). However, there is no requirement that the Manager and the Framer Devices be in the same SLIMbus Component.
The Manager and/or Framer Device shown in the upper left SLIMbus Component can also be incorporated into baseband and/or applications processors typically used to build mobile terminals.
Figure 8 below shows a conceptual view of a possible real world SLIMbus system. The "M" and "F" represents the Manager and Framer Devices respectively. Alternatively, the multi-mic array could replace the single mic in the system. Any mixture of audio related blocks could be attached.
Industry Standard Architecture (ISA) is the 16-bit internal bus of IBM PC/AT and similar computers based on the Intel 80286 and its immediate successors during the 1980s. The bus was (largely) backward compatible with the 8-bit bus of the 8088-based IBM PC, including the IBM PC/XT as well as IBM PC compatibles.
Peripheral Component Interconnect (PCI) is a local computer bus for attaching hardware devices in a computer and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any given processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. It is a parallel bus, synchronous to a single bus clock. Attached devices can take either the form of an integrated circuit fitted onto the motherboard or an expansion card that fits into a slot. The PCI Local Bus was first implemented in IBM PC compatibles, where it displaced the combination of several slow Industry Standard Architecture (ISA) slots and one fast VESA Local Bus (VLB) slot as the bus configuration. It has subsequently been adopted for other computer types. Typical PCI cards used in PCs include: network cards, sound cards, modems, extra ports such as Universal Serial Bus (USB) or serial, TV tuner cards and hard disk drive host adapters. PCI video cards replaced ISA and VLB cards until rising bandwidth needs outgrew the abilities of PCI. The preferred interface for video cards then became Accelerated Graphics Port (AGP), a superset of PCI, before giving way to PCI Express.
AES3 is a standard for the exchange of digital audio signals between professional audio devices. An AES3 signal can carry two channels of PCM audio over several transmission media including balanced lines, unbalanced lines, and optical fiber.
KNX is an open standard for commercial and domestic building automation. KNX devices can manage lighting, blinds and shutters, HVAC, security systems, energy management, audio video, white goods, displays, remote control, etc. KNX evolved from three earlier standards; the European Home Systems Protocol (EHS), BatiBUS, and the European Installation Bus. It can use twisted pair, powerline, RF, or IP links. On this network, the devices form distributed applications and tight interaction is possible. This is implemented via interworking models with standardised datapoint types and objects, modelling logical device channels.
A Controller Area Network is a robust vehicle bus standard designed to allow microcontrollers and devices to communicate with each other's applications without a host computer. It is a message-based protocol, designed originally for multiplex electrical wiring within automobiles to save on copper, but can also be used in many other contexts. For each device the data in a frame is transmitted sequentially but in such a way that if more than one device transmits at the same time the highest priority device is able to continue while the others back off. Frames are received by all devices, including by the transmitting device.
Electronic test equipment is used to create signals and capture responses from electronic devices under test (DUTs). In this way, the proper operation of the DUT can be proven or faults in the device can be traced. Use of electronic test equipment is essential to any serious work on electronics systems.
IEEE 802.15.4 is a technical standard which defines the operation of low-rate wireless personal area networks (LR-WPANs). It specifies the physical layer and media access control for LR-WPANs, and is maintained by the IEEE 802.15 working group, which defined the standard in 2003. It is the basis for the Zigbee, ISA100.11a, WirelessHART, MiWi, 6LoWPAN, Thread and SNAP specifications, each of which further extends the standard by developing the upper layers which are not defined in IEEE 802.15.4. In particular, 6LoWPAN defines a binding for the IPv6 version of the Internet Protocol (IP) over WPANs, and is itself used by upper layers like Thread.
LIN is a serial network protocol used for communication between components in vehicles. The need for a cheap serial network arose as the technologies and the facilities implemented in the car grew, while the CAN bus was too expensive to implement for every component in the car. European car manufacturers started using different serial communication technologies, which led to compatibility problems.
TURBOchannel is an open computer bus developed by DEC by during the late 1980s and early 1990s. Although it is open for any vendor to implement in their own systems, it was mostly used in Digital's own systems such as the MIPS-based DECstation and DECsystem systems, in the VAXstation 4000, and in the Alpha-based DEC 3000 AXP. Digital abandoned the use of TURBOchannel in favor of the EISA and PCI buses in late 1994, with the introduction of their AlphaStation and AlphaServer systems.
I²S, pronounced eye-squared-ess, is an electrical serial bus interface standard used for connecting digital audio devices together. It is used to communicate PCM audio data between integrated circuits in an electronic device. The I²S bus separates clock and serial data signals, resulting in simpler receivers than those required for asynchronous communications systems that need to recover the clock from the data stream. Alternatively I²S is spelled I2S or IIS. Despite the similar name, I²S is unrelated to the bidirectional I²C (IIC) bus.
Multichannel Audio Digital Interface (MADI) or AES10 is an Audio Engineering Society (AES) standard that defines the data format and electrical characteristics of an interface that carries multiple channels of digital audio. The AES first documented the MADI standard in AES10-1991, and updated it in AES10-2003 and AES10-2008. The MADI standard includes a bit-level description and has features in common with the two-channel AES3 interface.
McASP is an acronym for Multichannel Audio Serial Port, a communication peripheral found in Texas Instruments family of digital signal processors (DSPs) and Microcontroller Units (MCUs).
The McASP functions as a general-purpose audio serial port optimized for the needs of multichannel audio applications. Depending on the implementation, the McASP may be useful for time-division multiplexed (TDM) stream, Inter-Integrated Sound (I2S) protocols, and intercomponent digital audio interface transmission (DIT). However, some implementations are limited to supporting just the Inter-Integrated Sound (I2S) protocol.
The McASP consists of transmit and receive sections that may operate synchronized, or completely independently with separate master clocks, bit clocks, and frame syncs, and using different transmit modes with different bit-stream formats. The McASP module also includes up to 16 serializers that can be individually enabled to either transmit or receive. In addition, all of the McASP pins can be configured as general-purpose input/output (GPIO) pins.
The Display Serial Interface (DSI) is a specification by the Mobile Industry Processor Interface (MIPI) Alliance aimed at reducing the cost of display controllers in a mobile device. It is commonly targeted at LCD and similar display technologies. It defines a serial bus and a communication protocol between the host, the source of the image data, and the device which is the destination.
In mobile-telephone technology, the UniPro protocol stack follows the architecture of the classical OSI Reference Model. In UniPro, the OSI Physical Layer is split into two sublayers: Layer 1 and Layer 1.5 which abstracts from differences between alternative Layer 1 technologies. The actual physical layer is a separate specification as the various PHY options are reused in other MIPI Alliance specifications.
Consumer Electronics Control (CEC) is a feature of HDMI designed to control HDMI connected devices by using only one remote controller; so, individual CEC enabled devices can command and control each other without user intervention, for up to 15 devices. For example, a television set remote controller can also control a set-top box and a DVD player.
IEC 61334, known as Distribution automation using distribution line carrier systems, is a standard for low-speed reliable power line communications by electricity meters, water meters and SCADA. It is also known as spread frequency-shift keying (S-FSK) and was formerly known as IEC 1334 before IEC's most recent renumbering. It is actually a series of standards describing the researched physical environment of power lines, a well-adapted physical layer, a workable low-power media access layer, and a management interface. Related standards use the physical layer, but not the higher layers.
Media-accelerated Global Information Carrier (MaGIC) is an audio over Ethernet protocol developed by Gibson Guitar Corporation in partnership with 3COM. It allows bidirectional transmission of multichannel audio data, control data, and instrument power.
MOST is a high-speed multimedia network technology optimized by the automotive industry. It can be used for applications inside or outside the car. The serial MOST bus uses a daisy-chain topology or ring topology and synchronous data communication to transport audio, video, voice and data signals via plastic optical fiber (POF) or electrical conductor physical layers.
MIPI Alliance Debug Architecture provides a standardized infrastructure for debugging deeply embedded systems in the mobile and mobile-influenced space. The MIPI Alliance MIPI Debug Working Group has released a portfolio of specifications; their objective is to provide standard debug protocols and standard interfaces from a system on a chip (SoC) to the debug tool. The whitepaper Architecture Overview for Debug summarizes all the efforts. In recent years, the group focused on specifying protocols that improve the visibility of the internal operations of deeply embedded systems, standardizing debug solutions via the functional interfaces of form factor devices, and specifying the use of I3C as debugging bus.
I3C is a specification to enable communication between computer chips by defining the electrical connection between the chips and signaling patterns to be used. The standard defines the electrical connection between the chips to be a two wire, shared(multidrop), serial data bus, one wire (SCL
) being used as a clock to define the sampling times, the other wire (SDA
) being used as a data line whose voltage can be sampled. The standard defines a signalling protocol in which multiple chips can control communication and thereby act as the bus master.
A partial list of SLIMbus implementer information can be found at the following: