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Programmer’s Reference Manual 45
Intel
®
High Definition Audio Controller Registers (D27:F0)
1.2.11 INSTRMPAY—Input Stream Payload Capability
(Intel
®
High Definition Audio Controller—D27:F0)
Memory Address: HDBAR + 1Ah Attribute: RO
Default Value: 0018h Size: 16 bits
Bit Description
15:14
Input FIFO Padding Type (IPADTYPE)— RO: This field indicates how the controller pads the
samples in the controller's buffer (FIFO). Controllers may not pad at all or may pad to byte or
memory container sizes.
0h = Controller pads all samples to bytes
1h = Reserved
2h = Controller pads to memory container size
3h = Controller does not pad and uses samples directly
13:0
Input Stream Payload Capability (INSTRMPAY)— RO: This field indicates the maximum number
of Words per frame for any single input stream. This measurement is in 16-bit Word quantities per
48-kHz frame. The maximum supported is 24 Words (48B); therefore, a value of 18h is reported in
this register.
The value does not specify the number of words actually transmitted in the frame, but is the size of
the data as it will be placed into the controller's buffer (FIFO). Thus, samples will be padded
according to IPADTYPE before being stored into controller buffer. To compute the supported
streams, each sample is padded according to IPADTYPE and then multiplied by the number of
channels and samples per frame. If this computed value is larger than INSTRMPAY, then that
stream is not supported. As the inbound stream tag is not stored with the samples it is not included
in the word count.
The value may be larger than INPAY register value in some cases, although values less than INPAY
may also be invalid due to overhead. Software must ensure that a format that would cause more
Words per frame than indicated is not programmed into the Input Stream Descriptor Register.