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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
453 of 808
NXP Semiconductors
UM10360
Chapter 20: LPC17xx I2S interface
5.9 Transmit Clock Rate register (I2STXRATE - 0x400A 8020)
The MCLK rate for the I
2
S transmitter is determined by the values in the I2STXRATE
register. The required I2STXRATE setting depends on the desired audio sample rate
desired, the format (stereo/mono) used, and the data size.
I2STXMCLK = PCLK * (X/Y) /2
Note: If the value of X = 0, then no clock is generated.
5.10 Receive Clock Rate register (I2SRXRATE - 0x400A 8024)
The MCLK rate for the I
2
S receiver is determined by the values in the I2SRXRATE
register. The required I2SRXRATE setting depends on the peripheral clock rate (PCLK)
and the desired MCLK rate (such as 256 fs).
I2SRXMCLK = PCLK * (X/Y) /2
Note: If the value of X = 0, then no clock is generated.
15:13
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
20:16
tx_depth_Irq
Set the FIFO level on which to create an irq request.
0
31:21
-
Reserved, user software should not write ones to reserved
bits. The value read from a reserved bit is not defined.
NA
Table 393: Interrupt Request Control register (I2SIRQ - address 0x400A 801C) bit description
Bit
Symbol
Description
Reset
Value
Table 394: Transmit Clock Rate register (I2TXRATE - address 0x400A 8020) bit description
Bit
Symbol
Description
Reset
Value
7:0
Y_divider
I
2
S
transmit MCLK rate denominator. This value is used to divide
PCLK to produce the transmit MCLK. Eight bits of fractional divide
supports a wide range of possibilities. A value of zero stops the
clock.
0
15:8
X_divider
I
2
S
transmit MCLK rate numerator. This value is used to multiply
PCLK by to produce the transmit MCLK. A value of zero stops the
clock. Eight bits of fractional divide supports a wide range of
possibilities. Note: the resulting ratio X/Y is divided by 2.
0
31:16
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
NA