SAM4L Datasheet, PDF (774/1185 Pages) ATMEL Corporation – ATSAM ARM-based Flash MCU

ATSAM4L4/L2
29.5.3 Clocks
The clock for the IISC bus interface (CLK_IISC) is generated by the Power Manager. It is recom-
mended to disable the IISC before disabling the clock, to avoid freezing the IISC in an undefined
state.
One of the generic clocks is connected to the IISC. The generic clock (GCLK_IISC) can be set to
a wide range of frequencies and clock sources. The GCLK_IISC must be enabled and config-
ured before use. Refer to the module configuration section for details on the GCLK_IISC used
for the IISC. The frequency for this clock has to be set as described in Table.
29.5.4 DMA
The IISC DMA handshake interfaces are connected to the Peripheral DMA Controller. Using the
IISC DMA functionality requires the Peripheral DMA Controller to be programmed first.
29.5.5 Interrupts
The IISC interrupt line is connected to the Interrupt Controller. Using the IISC interrupt requires
the Interrupt Controller to be programmed first.
29.5.6
Debug Operation
When an external debugger forces the CPU into debug mode, the IISC continues normal opera-
tion. If this module is configured in a way that requires it to be periodically serviced by the CPU
through interrupt requests or similar, improper operation or data loss may result during
debugging.
29.6 Functional Description
29.6.1
Initialization
The IISC features a Receiver, a Transmitter, and, for Master and Controller modes, a Clock
Generator. Receiver and Transmitter share the same Serial Clock and Word Select.
Before enabling the IISC, the chosen configuration must be written to the Mode Register (MR).
The IMCKMODE, MODE, and DATALENGTH fields in the MR register must be written. If the
IMCKMODE field is written as one, then the IMCKFS field should be written with the chosen
ratio, as described in Section 29.6.5 ”Serial Clock and Word Select Generation” on page 776.
Once the Mode Register has been written, the IISC Clock Generator, Receiver, and Transmitter
can be enabled by writing a one to the CKEN, RXEN, and TXEN bits in the Control Register
(CR). The Clock Generator can be enabled alone, in Controller Mode, to output clocks to the
IMCK, ISCK, and IWS pins. The Clock Generator must also be enabled if the Receiver or the
Transmitter is enabled.
The Clock Generator, Receiver, and Transmitter can be disabled independently by writing a one
to CR.CXDIS, CR.RXDIS and/or CR.TXDIS respectively. Once requested to stop, they will only
stop when the transmission of the pending frame transmission will be completed.
29.6.2
Basic Operation
The Receiver can be operated by reading the Receiver Holding Register (RHR), whenever the
Receive Ready (RXRDY) bit in the Status Register (SR) is set. Successive values read from
RHR will correspond to the samples from the left and right audio channels for the successive
frames.
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