NXP Semiconductors LPC2880, Руководство пользователя

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UM10208_2 © NXP B.V. 2007. All rights reserved.
User manual Rev. 02 — 1 June 2007 259 of 362
1. Features
•
I
2
S output via Digital Analog Out (DAO) module
•
Digital values 16 to 24 bits
•
Streaming Analog Out (SAO) module provides FIFO buffering
•
DMA or processor transfer
2. Description
The LPC288x can output a single- or dual-channel audio stream to an Inter-IC Sound
(I
2
S) bus. The I
2
S output module is called the DAO. It can output serial data in standard
Philips IIS format, or in right-justified 16-, 18-, 20-, or 24-bit format.
Because the ARM7 microcontroller services a variety of tasks in an interleaved fashion
that involves worst-case event-arrival considerations, a FIFO buffer called an SAO is
included to smooth the transfer of the digital values from memory to the DAO. This
transfer can be performed by the processor or by GPDMA channel(s).
3. DAO pins
The DAO has three dedicated pins, as shown in Table 20–292 .
4. DAO registers
Table 20–293 lists the LPC288x registers associated with I
2
S output. Subsequent
sections describe the registers in greater detail.
UM10208
Chapter 20: I
2
S output module (DAO)
Rev. 02 — 1 June 2007 User manual
Table 292. DAO pins
Name Type Description
BCKO / P3[5] Output Bit clock
DATO / P3[6] Output Serial Data
WSO Output Word select. This signal distinguishes L data from R data.
Table 293. DAO registers
Name Address Description Access Reset
value
SIOCR 0x8020 0384 Stream I/O Configuration Register. This register
is shared with the Dual ADC, I
2
S in, and Dual DAC
blocks. The bits in this register that affect the DAO
have fixed/prescribed values.
R/W 0x180
I2S_FMT 0x8020 0380 I
2
S Format Register. This register is shared with
the DAI block. For the DAO, it controls how data is
output on the DATO pin.
R/W 0xDD