Production Data
WM8805
ERROR HANDLING IN SOFTWARE MODE
When the TRANS_ERR flag is asserted, it indicates that the recovered Rx S/PDIF sub-frame is
corrupted. This corruption can due to a BI-Phase error, a parity error or a pre-amble error. When the
INVALID flag is asserted, it indicates that the recovered Rx S/PDIF sub-frame has been marked as
being invalid by the source of the S/PDIF data. Both TRANS_ERR and INVALID indicate an error.
The S/PDIF receiver has two modes of handling for these errors, manual and automatic. The
mechanism for each flag is similar. The mechanisms are described below.
MANUAL ERROR HANDLING
This manual handling of errored Rx S/PDIF data can be used when an application processor is being
interrupted via the INT_N signal. Appropriate action should be taken by the application processor to
handle the error condition
If the TRANS_ERR and INVALID error flags are not masked using the MASK register, the recovered
S/PDIF Rx data is passed to the digital audio interface or to the S/PDIF transmitter irrespective of the
state of the flag and the data content of the recovered stream.(Also refer to note below). In this case,
the application processor will be interrupted via the INT_N signal.
AUTOMATIC ERROR HANDLING
This automatic handling of errored Rx S/PDIF data can be used when an application processor is not
being interrupted via the INT_N signal leaving the WM8805 to handle the error condition.
If the TRANS_ERR and INVALID error flags are masked using the MASK register, the WM8805
output data from the S/PDIF Rx interface depends on the setting of FILLMODE. If FILLMODE=1,
then the incoming data (which is errored) is overwritten with 0’s. If FILLMODE=0, then the last valid
data sample is repeatedly output.
For the INVALID flag, the automatic error handling can be disabled if ALWAYSVALID =1. If
ALWAYSVALID is set, then the recovered Rx S/PDIF data, which is marked as invalid, will be
allowed to pass to the digital audio interface or to the S/PDIF transmitter. The data will not be
modified in any way.
Note:
For the S/PDIF receiver to S/PDIF transmitter data path, only the INVALID flag will cause data to be
overwritten, the TRANS_ERR flag is not used to overwrite data which is passed to the S/PDIF
transmitter.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
R8
PLL6
08h
5
FILLMODE
0
Fill Mode Overwrite Configuration
Determines S/PDIF receiver action when TRANS_ERR or
INVALID flag is masked and error condition sets the flag:
0 = Data from S/PDIF receiver is overwritten with last valid
data sample when flag is set.
1 = Data from S/PDIF receiver is overwritten as all zeros
when flag is set.
6
ALWAYSVALID
0
Automatic Error Handling Configuration for INVALID
Flag
0 = INVALID flag automatic error handling enabled.
1 = INVALID flag automatic error handling disabled.
Table 51 S/PDIF Receiver Automatic Error Handling Configuration Registers
PD Rev 4.1 September 07
43
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
