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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
461 of 808
NXP Semiconductors
UM10360
Chapter 20: LPC17xx I2S interface
8.
FIFO controller
Handling of data for transmission and reception is performed via the FIFO controller which
can generate two DMA requests and an interrupt request. The controller consists of a set
of comparators which compare FIFO levels with depth settings contained in registers. The
current status of the level comparators can be seen in the APB status register.
System signaling occurs when a level detection is true and enabled.
Fig 110. 4-wire receiver slave mode sharing the transmitter bit clock and WS
I2SRX_WS
I2SRX_SDA
TX bit clock
TX_WS ref
I
2
S
peripheral
block
(receive)
Table 402. Conditions for FIFO level comparison
Level Comparison
Condition
dmareq_tx_1
tx_depth_dma1 >= tx_level
dmareq_rx_1
rx_depth_dma1 <= rx_level
dmareq_tx_2
tx_depth_dma2 >= tx_level
dmareq_rx_2
rx_depth_dma2 <= rx_level
irq_tx
tx_depth_irq >= tx_level
irq_rx
rx_depth_irq <= rx_level
Table 403. DMA and interrupt request generation
System Signaling
Condition
irq
(irq_rx & rx_irq_enable) | (irq_tx & tx_irq_enable
dmareq[0]
(dmareq_tx_1 & tx_dma1_enable ) | (dmareq_rx_1 &
rx_dma1_enable )
dmareq[1]
( dmareq_tx_2 & tx_dma2_enable ) | (dmareq_rx_2 &
rx_dma2_enable )
Table 404. Status feedback in the I2SSTATE register
Status Feedback
Status
irq
irq_rx | irq_tx
dmareq1
(dmareq_tx_1 | dmareq_rx_1)
dmareq2
(dmareq_rx_2 | dmareq_tx_2)