WM8281ECSSLASHR datasheet(169/392 Pages) CIRRUS

169 / 392 page

WM8281

Rev 4.0

169

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.

The REPORT_INFORMATION (EC, IS) message is used to inform other devices about a change in a

specified element in the Information Map. The payload of this message contains the Element Code

(EC) and the Information Slice (IS). The Information Slice byte(s) contain the new value of the

applicable parameter.

VALUE MANAGEMENT (INCLUDING REGISTER ACCESS)

A memory map of Value Elements is defined for each Device. This is arranged in 3 x 1kByte blocks,

comprising Core Value elements, Device Class-specific Value elements, and User Value elements

respectively, as described in the MIPI specification. These elements are typically parameters used to

configure Device behaviour.

The User Value elements of the Interface Device are used on WM8281 to support Read/Write access

to the Register Map. Details

of how to access specific registers are described in the “SLIMbus

Interface Control

” section.

Note that, with the exception of the User Value elements of the Interface Device, the contents of the

User Value portion for each WM8281 SLIMbus Device are reserved.

Read/Write access is implemented using the messages described below. Specific elements within the

Value 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_VALUE (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 REPLY_VALUE (TID, VS) message is used to provide readback of a requested parameter. The

payload of this message contains the Transaction ID (TID) and the Value Slice (VS). The Value Slice

byte(s) contain the value of the requested parameter.

The CHANGE_VALUE (EC, VU) message is used to write data to a specified element in the Value

Map. The payload of this message contains the Element Code (EC) and the Value Update (VU). The

Value Update byte(s) contain the new value of the applicable parameter.

FRAME & CLOCKING MANAGEMENT

This section describes the SLIMbus messages associated with changing the Frame or Clocking

configuration. One or more configuration messages may be issued as part of a Reconfiguration

Sequence; all of the updated parameters become active at once, when the Reconfiguration boundary

is reached.

The BEGIN_RECONFIGURATION message is issued to define a Reconfiguration Boundary point:

subsequent NEXT_* messages will become active at the first valid Superframe boundary following

receipt of the RECONFIGURE_NOW message. (A valid boundary must be at least two Slots after the

end of the RECONFIGURE_NOW message.) Both of these messages have no payload content.

The NEXT_ACTIVE_FRAMER (LAIF, NCo, NCi) message is used to select a new device as the

active Framer. The payload of this message includes the Logical Address, Incoming Framer (LAIF).

Two other fields (NCo, NCi) define the number of clock cycles for which the CLK line shall be inactive

during the handover.

The NEXT_SUBFRAME_MODE (SM) and NEXT_CLOCK_GEAR (CG) messages are used to re-

configure the SLIMbus clocking or framing definition. The payload of each is the respective Subframe

Mode (SM) or Clock Gear (CG) respectively.

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