Analog Devices SHARC ADSP-21368 - Interrupted Data Streams on the Receiver

ADSP-21368 SHARC Processor Hardware Reference 9-27
S/PDIF Transmitter/Receiver
Interrupted Data Streams on the Receiver
When using the SPDIF receiver with data streams that are likely to be
interrupted, (in other words unplugged and reconnected), it is necessary
to take some extra steps to ensure that the SPDIF receiver’s digital PLL
will re lock to the stream. The steps to accomplish this are described
below.
1. Setup interrupts within the DAI so that the SPDIF RX can gener-
ate an interrupt when the stream is reconnected.
2. Within the interrupt service routine (ISR), stop and restart the dig-
ital PLL. This is accomplished by setting and then clearing bit 7 of
the SPDIF receiver control register.
3. Return from the ISR and continue normal operation.
This method of resetting the digital PLL has been shown to provide
extremely reliable performance when SPDIF inputs that are interrupted or
unplugged momentarily occur.
The following procedure and the example code show how to reset the dig-
ital PLL. Note that all of the SPDIF receiver interrupts are handled
through the DAI interrupt controller. For more information, see
“DAI/DPI Interrupt Controller” on page 4-65.
1. Initialize the No Stream Interrupt
/* Enable interrupts (globally) */
BIT SET MODE1 IRPTEN;
/* unmask DAI Hi=Priority Interrupt */
bit set imask DAIHI;
ustat1 = DIR_NOSTREAM_INT;
/* Enable no-stream Interrupt on Falling Edge. Interrupt
occurs when the stream is reconnected */
dm(DAI_IRPTL_FE) = ustat1;