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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1210 of 1441
NXP Semiconductors
UM10503
Chapter 44: LPC43xx/LPC43Sxx I2S interface
44.6.8 I2S Interrupt Request Control register
The IRQ register controls the operation of the I2S interrupt request. The function of bits in
IRQ are shown in
.
44.6.9 I2S Transmit Clock Rate register
The MCLK rate for the I2S transmitter is determined by the values in the TXRATE register.
The required TXRATE setting depends on the desired audio sample rate, the format
(stereo/mono) used, and the data size.
The transmitter MCLK rate is generated using a fractional rate generator, dividing down
the frequency of PCLK = CLK_APB1_I2S. Values of the numerator (X) and the
denominator (Y) must be chosen to produce a frequency twice that desired for the
transmitter MCLK, which must be an integer multiple of the transmitter bit clock rate.
Fractional rate generators have some aspects that the user should be aware of when
choosing settings. These are discussed in
. The equation for the
fractional rate generator is:
I2S_TX_MCLK = PCLK * (X/Y) /2
Note: If the value of X or Y is 0, then no clock is generated. Also, the value of Y must be
greater than or equal to X.
15:12
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
-
19:16
TX_DEPTH_DMA2
Set the FIFO level that triggers a transmit DMA request
on DMA2.
0
31:20
-
Reserved, user software should not write ones to
reserved bits. The value read from a reserved bit is not
defined.
-
Table 1007.I2S DMA Configuration register 2 (DMA2, address 0x400A 2018 (I2S0) and 0x400A
3018 (I2S1)) bit description
Bit
Symbol
Description
Reset
value
Table 1008.I2S Interrupt Request Control register (IRQ, address 0x400A 201C (I2S0) and
0x400A 301C (I2S1)) bit description
Bit
Symbol
Description
Reset
value
0
RX_IRQ_ENABLE
When 1, enables I2S receive interrupt.
0
1
TX_IRQ_ENABLE
When 1, enables I2S transmit interrupt.
0
7:2
-
Reserved.
0
11:8
RX_DEPTH_IRQ
Set the FIFO level on which to create an irq request.
0
15:12
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
-
19:16
TX_DEPTH_IRQ
Set the FIFO level on which to create an irq request.
0
31:20
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
-