NXP Semiconductors LPC24XX UM10237 - Manual (Page 410)

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User manual Rev. 04 — 26 August 2009 410 of 792
NXP Semiconductors
UM10237
Chapter 15: LPC24XX USB OTG controller
7.15 I2C Clock Low Register (I2C_CLKLO - 0xFFE0 C310)
The CLK register holds a terminal count for counting 48 MHz clock cycles to create the
low period of the slower I
2 C serial clock, SCL.
7.16 Interrupt handling
The interrupts set in the OTGIntSt register are set and cleared during HNP switching. All
OTG related interrupts, if enabled, are routed to the USB_OTG_INT bit in the USBIntSt
register.
I2C related interrupts are set in the I2C_STS register and routed, if enabled by I2C_CTL,
to the USB_I2C_INT bit.
For more details on the interrupts created by device controller, see the USB device
chapter. For interrupts created by the host controllers, see the OHCI specification.
The EN_USB_INTS bit in the USBIntSt register enables the routing of any of the USB
related interrupts to the VIC controller (see
Figure 15–58 ).
Remark: During the HNP switching between host and device with the OTG stack active,
an action may raise several levels of interrupts. It is advised to let the OTG stack initiate
any actions based on interrupts and ignore device and host level interrupts. This means
that during HNP switching, the OTG stack provides the communication to the host and
device controllers.
Table 375. I2C_CLKLO register (I2C_CLKLO - address 0xFFE0 C310) bit description
Bit Symbol Description Reset
Value
7:0 CDLO Clock divisor low. This value is the number of 48 MHz
clocks the serial clock (SCL) will be low. 0xB9
Fig 58. USB OTG interrupt handling
USB_INT_REQ_HP
USB_INT_REQ_LP
USB_INT_REQ_DMA
EN_USB_INTS
to VIC
channel #22
USB_HOST_INT
USB_OTG_INT
USB_I2C_INT
USB_NEED_CLOCK
USBIntSt
USB DEVICE
INTERRUPTS
USB HOST
INTERRUPTS
OTGIntSt
TMR
REMOVE_PU
HNP_SUCCESS
HNP_FAILURE
USB I2C
INTERRUPTS