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<concept id="GUID-052F58B7-117B-5EDD-A3D5-CB0DE6A4E239" xml:lang="en"><title>IIC Kernel-side

Implementation Guide: Generic Considerations</title><shortdesc>This document explains how to implement an interface from Symbian

platform to an IIC bus.</shortdesc><prolog><metadata><keywords/></metadata></prolog><conbody>

<section id="GUID-C3EE341A-BEAB-4E0C-A91E-7A1A285BCE96"><title>Purpose</title> <p>This document covers information which

is generic to master and slave channel implementation </p> <p><b>Intended

Audience</b> </p> <p>Base porting engineers. </p> <p><b>Introduction</b> </p> <p>IIC

buses (serial inter-chip buses) are a class of bus used to transmit non time-critical

data between components of a hardware system. </p> </section>

<section id="GUID-38B543E8-06DB-417F-8B8E-84F6B43DF8BF"><title>Generic architecture</title> <p>Different IIC buses have a

large amount of functionality in common, but some functionality is specific

to individual implementations. For this reason, the Symbian platform IIC library

has an architecture consisting of two layers, the Platform Independent Layer

(PIL) and the Platform Specific Layer (PSL). The Platform Independent Layer

is a set of classes which encapsulate generic functionality and have been

implemented for you. The Platform Specific Layer is an interface which you

must implement yourself to encapsulate the functionality specific to the platform

you are working on. </p> <p>You implement the Platform Specific Layer by subclassing

the classes of the Platform Independent Layer and writing certain functions

using the machine instructions of your hardware. To access the hardware you

are strongly recommended to use the Symbian platform API (e.g. <xref href="GUID-66BB033A-3386-3913-9A25-EF3867D42C2C.dita"><apiname>AsspRegister</apiname></xref> to

access hardware registers, or <xref href="GUID-C93C53D3-2BE8-36AE-83B8-4CDB4195649B.dita"><apiname>GPIO</apiname></xref> to access GPIO pins). </p> <p>An

IIC channel operates in one of two modes, master and slave, and there are

separate master and slave APIs to be implemented. In master mode, a channel

and a client communicating with that channel execute in two separate threads.

In slave mode there is only one thread for both channel and client. </p> <p>The

platform specific and platform independent APIs assume an interrupt-driven

approach to implementation. An event on hardware triggers an interrupt, which

then signals this event to the channel thread (where client is master) or

client thread (where client is slave). This means that implementation involves

writing interrupt service routines (ISRs) and a DFC queue to hold the callbacks

which respond to them. A channel responds to interrupts by requesting notification

of a hardware event, specified in the form of a bitmask called a trigger (slave)

or reacting to it by receiving or transmitting data (master) or by various

other possible responses. The possible triggers and possible responses to

them constitute a state machine. A master channel conforms to a simple state

machine which varies from one hardware implementation to another. A slave

channel conforms to a more complex state machine, generic to all implementations,

which is explained in this document. </p> <p>Symbian platform provides an

example of an IIC channel in the Naviengine reference implementatin which

you are encouraged to consult and use as a model. </p> <p><b>API Conditions</b> </p> <p>The

same conditions apply to all APIs, both master and slave. They are: </p> <ul>

<li id="GUID-EBBE18CB-D8FE-5BA6-98F4-C5AABB87731D"><p>Kernel must be unlocked. </p> </li>

<li id="GUID-6CD66E54-61A6-5C80-AFDE-3C42DA13D75C"><p>No fast mutex must be

held. </p> </li>

<li id="GUID-2535DF51-CE96-5F12-89AB-AE15BD1CB6EA"><p>Interrupts must be enabled. </p> </li>

<li id="GUID-8DF80532-D047-5160-BDAE-2CF68642D5D9"><p>APIs are called from

thread context (not from NULL thread or DFC thread 1). </p> </li>

</ul> </section>

</conbody><related-links>

<link href="GUID-0C8318B1-71D7-5384-97EB-85CBBC3E6B84.dita"><linktext>IIC Kernel-side

Implementation Guide:                 Master Channel</linktext></link>

<link href="GUID-C9644081-004E-5DA0-8133-A32EEA91EF5E.dita"><linktext>IIC Kernel-side

Implementation Guide:                 Slave Channel</linktext></link>

<link href="GUID-9986DCC6-EE73-59FB-BDAC-9B09DC64FBCE.dita"><linktext>Client of

Master Channel Implementation Tutorial</linktext></link>

<link href="GUID-F461CBB3-F8D1-5961-AD51-5741143A1CB1.dita"><linktext>Client of

Slave Channel Implementation Tutorial</linktext></link>

<link href="GUID-B2F86F54-EF50-56DB-ADF7-15325AC9324D.dita"><linktext>IIC Guide</linktext>

</link>

<link href="GUID-99FC067C-0AED-5373-AF63-8DB7FF5C1F7E.dita"><linktext>SPI Technology

Guide</linktext></link>

<link href="GUID-3A30DA16-ECA8-5639-A9DC-6BE2AD55420B.dita"><linktext>I2C Technology

Guide</linktext></link>