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UM10503
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© NXP B.V. 2015. All rights reserved.
User manual
Rev. 2.1 — 10 December 2015
1212 of 1441
NXP Semiconductors
UM10503
Chapter 44: LPC43xx/LPC43Sxx I2S interface
44.6.11 I2S Transmit Clock Bit Rate register
The bit rate for the I2S transmitter is determined by the value of the TXBITRATE register.
The value depends on the audio sample rate desired and the data size and format
(stereo/mono) used. For example, a 48 kHz sample rate for 16-bit stereo data requires a
bit rate of 48 000 x 16 x 2 = 1.536 MHz.
44.6.12 I2S Receive Clock Bit Rate register
The bit rate for the I2S receiver is determined by the value of the RXBITRATE register.
The value depends on the audio sample rate, as well as the data size and format used.
The calculation is the same as for TXBITRATE.
44.6.13 I2S Transmit Mode Control register
The Transmit Mode Control register contains additional controls for the transmit clock
source, enabling the 4-pin mode
(SCK and WS signals are shared between I2S transmit and
receive blocks)
, and how MCLK is used.
Table 1010.I2S Receive Clock Rate register (RXRATE, address 0x400A 2024 (I2S0) and
0x400A 3024 (I2S1)) bit description
Bit
Symbol
Description
Reset
value
7:0
Y_DIVIDER
I2S receive MCLK rate denominator. This value is used to divide
PCLK to produce the receive MCLK. Eight bits of fractional divide
supports a wide range of possibilities. A value of 0 stops the clock.
0
15:8
X_DIVIDER
I2S receive MCLK rate numerator. This value is used to multiply
PCLK by to produce the receive MCLK. A value of 0 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.
-
Table 1011.I2S Transmit Clock Rate register (TXBITRATE, address 0x400A 2028 (I2S0) and
0x400A 3028 (I2S1)) bit description
Bit
Symbol
Description
Reset
value
5:0
TX_BITRATE
I2S transmit bit rate. This value plus one is used to divide
TX_MCLK to produce the transmit bit clock.
0
31:6
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-
Table 1012.I2S Receive Clock Rate register (RXBITRATE, address 0x400A 202C (I2S0) and
0x400A 302C (I2S1)) bit description
Bit
Symbol
Description
Reset
value
5:0
RX_BITRATE
I2S receive bit rate. This value plus one is used to divide
RX_MCLK to produce the receive bit clock.
0
31:6
-
Reserved, user software should not write ones to reserved bits.
The value read from a reserved bit is not defined.
-