WM8998 Datasheet, PDF (127/307 Pages) Wolfson Microelectronics plc – High Performance Audio Hub CODEC

Production Data
WM8998
SLIMBUS CONTROL SEQUENCES
This section describes the messages and general protocol associated with most aspects of the
SLIMbus system.
Note that the SLIMbus specification permits some flexibility in Core Message support for different
components. See “SLIMbus Interface Control” for details of which message(s) are supported on each
of the SLIMbus devices that are present on the WM8998.
DEVICE MANAGEMENT & CONFIGURATION
This section describes the SLIMbus messages associated with configuring all devices on the SLIMbus
interface.
When the SLIMbus interface starts up, it is required that one (and only one) of the components
provides the Manager and Framer Device functions. Other devices can request connection to the bus
after they have gained synchronisation.
The REPORT_PRESENT (DC, DCV) message may be issued by devices attempting to connect to
the bus. The payload of this message contains the Device Class (DC) and Device Class Version
(DCV) parameters, describing the type of device that is attempting to connect. This message may be
issued autonomously by the connecting device, or else in response to a
REQUEST_SELF_ANNOUNCEMENT message from the Manager Device.
After positively acknowledging the REPORT_PRESENT message, the Manager Device will then issue
the ASSIGN_LOGICAL_ADDRESS (LA) message to allow the other device to connect to the bus.
The payload of this message contains the Logical Address (LA) parameter only; this is the unique
address by which the connected device will send and receive SLIMbus messages. The device is then
said to be ‘enumerated’.
Once a device has been successfully connected to the bus, the Logical Address (LA) parameter can
be changed at any time using the CHANGE_LOGICAL_ADDRESS (LA) message.
The RESET_DEVICE message commands an individual SLIMbus device to perform its reset
procedure. As part of the reset, all associated ports will be reset, and any associated Data Channels
will be cancelled. Note that, if the RESET_DEVICE command is issued to an Interface Device, it will
cause a Component Reset (ie. all Devices within the associated component are reset). Under a
Component Reset, every associated Device will release its Logical Address, and the Component will
become disconnected from the bus.
INFORMATION MANAGEMENT
A memory map of Information Elements is defined for each Device. This is arranged in 3 x 1kByte
blocks, comprising Core Information elements, Device Class-specific Information elements, and User
Information elements respectively, as described in the MIPI specification. Note that the contents of the
User Information portion for each WM8998 SLIMbus Device are reserved.
Read/Write access is implemented using the messages described below. Specific elements within the
Information Map are identified using the Element Code (EC) parameter. In the case of Read access, a
unique Transaction ID (TID) is assigned to each message relating to a particular read/write request.
The REQUEST_INFORMATION (TID, EC) message is used to instruct a device to respond with the
indicated information. The payload of this message contains the Transaction ID (TID) and the Element
Code (EC).
The REQUEST_CLEAR_INFORMATION (TID, EC, CM) message is used to instruct a device to
respond with the indicated information, and also to clear all, or parts, of the same information slice.
The payload of this message contains the Transaction ID (TID), Element Code (EC), and Clear Mask
(CM). The Clear Mask field is used to select which element(s) are to be cleared as part of the
instruction.
The REPLY_INFORMATION (TID, IS) message is used to provide readback of a requested
parameter. The payload of this message contains the Transaction ID (TID) and the Information Slice
(IS). The Information Slice byte(s) contain the value of the requested parameter.
The CLEAR_INFORMATION (EC, CM) message is used to clear all, or parts, of the indicated
information slice. The payload of this message contains the Element Code (EC) and Clear Mask
(CM). The Clear Mask field is used to select which element(s) are to be cleared as part of the
instruction.
w
PD, October 2014, Rev 4.0
127