SLIMbus

Key takeaways

SLIMbus belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect SLIMbus to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of SLIMbus from memory before moving on to harder problems.

Reference excerpt

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. 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, and SSI (Synchronous Serial Interface for digital audio), as well as some instances of many digital control buses such as I2C, SPI, microWire, UART, or GPIO pins on the digital audio components.

History The MIPI Alliance was formed in fall of 2003. Interface architecture including a low speed media link bus (LowML) presented at the F2F meeting of MIPI Alliance in Sophia Antipolis, France in March, 2004. LML Investigation Group (LML-IG) created in July 2004 by the MIPI Alliance. First meeting was a teleconference on August 3, 2004. LML Working Group (LML-WG) created in Q4 2004. LML WG Charter submitted to the MIPI Board in December, 2004. First meeting as a full Working Group on April 12, 2005. LML-WG released first draft of SLIMbus with text in all chapters (v0.55) on October 18, 2005. SLIMbus specification v1.00 was released to adopters on May 16, 2007. From June 2007 to June 2008, SLIMbus specification improvement (ambiguities, typos & bugs fixed) based on implementer feed-back. SLIMbus specification V1.01 was released to adopters on December 3, 2008 and is recommended for implementation.

SLIMbus Devices and Device Classes 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.

Manager Device 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.

Framer Device 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.

Interface Device 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.

Generic Device (Function) 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).

SLIMbus Component 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.

SLIMbus DATA and CLK 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.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with SLIMbus

Start with the simplest possible case. Write down what SLIMbus claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to SLIMbus before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about SLIMbus ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of SLIMbus

In research: SLIMbus appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses SLIMbus in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: SLIMbus is common in secondary-school and first-year university syllabi. It links to neighbouring topics Computer buses, MIPI Alliance standards, so understanding it makes those chapters shorter.
In everyday life: Look for SLIMbus outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study SLIMbus in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what SLIMbus means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain SLIMbus out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is SLIMbus in simple terms?

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.

Why does SLIMbus matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study SLIMbus?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on SLIMbus.