NXP Semiconductors LPC24XX UM10237 - Manual (Page 406)

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User manual Rev. 04 — 26 August 2009 406 of 792
NXP Semiconductors
UM10237
Chapter 15: LPC24XX USB OTG controller
7.10 I2C Receive Register (I2C_RX - 0xFFE0 C300)
This register is the top byte of the receive FIFO. The receive FIFO is 4 bytes deep. The Rx
FIFO is flushed by a hard reset or by a soft reset (I2C_CTL bit 7). Reading an empty FIFO
gives unpredictable data results.
7.11 I2C Transmit Register (I2C_TX - 0xFFE0 C300)
This register is the top byte of the transmit FIFO. The transmit FIFO is 4 bytes deep.
The Tx FIFO is flushed by a hard reset, soft reset (I2C_CTL bit 7) or if an arbitration failure
occurs (I2C_STS bit 3). Data writes to a full FIFO are ignored.
I2C_TX must be written for both write and read operations to transfer each byte. Bits [7:0]
are ignored for master-receive operations. The master-receiver must write a dummy byte
to the TX FIFO for each byte it expects to receive in the RX FIFO. When the STOP bit is
set or the START bit is set to cause a RESTART condition on a byte written to the TX
FIFO (master-receiver), then the byte read from the slave is not acknowledged. That is,
the last byte of a master-receive operation is not acknowledged.
7.12 I2C Status Register (I2C_STS - 0xFFE0 C304)
The I2C_STS register provides status information on the TX and RX blocks as well as the
current state of the external buses. Individual bits are enabled as interrupts by the
I2C_CTL register and routed to the I2C_USB_INT bit in USBIntSt.
4 AHB_CLK_ON AHB master clock status. 0
0 AHB clock is not available.
1 AHB clock is available.
31:5 - NA Reserved, user software should not write ones
to reserved bits. The value read from a
reserved bit is not defined. NA
Table 369. OTG_clock_status register (OTGClkSt - address 0xFFE0 CFF8) bit description
Bit Symbol Value Description Reset
Value
Table 370. I2C Receive register (I2C_RX - address 0xFFE0 C300) bit description
Bit Symbol Description Reset
Value
7:0 RX Data Receive data. -
Table 371. I2C Transmit register (I2C_TX - address 0xFFE0 C300) bit description
Bit Symbol Description Reset
Value
7:0 TX Data Transmit data. -
8 START When 1, issue a START condition before transmitting this byte. -
9 STOP When 1, issue a STOP condition after transmitting this byte. -
31:10 - Reserved. User software should not write ones to reserved bits. The
value read from a reserved bit is not defined. -