MCF5272 Datasheet, PDF (440/550 Pages) Motorola, Inc – MCF5272 ColdFire Integrated Microprocessor Users Manual

USB Module Signals and PA[6:0]
19.11.6 USB Transmitter Output Enable (USB_TxEN/PA5)
USB mode: USB_TxEN enables the transceiver to transmit data on the bus. It requires a
4.7-KΩ pullup resistor to ensure that the external USB Tx driver is off between the
MCF5272 coming out of reset and initializing the port A pin configuration register.
Port A mode: This pin can also be configured as the PA5 I/O.
19.11.7 USB Rx Data Output (USB_RxD/PA6)
USB mode: USB_RxD is the receive data output from the differential receiver inputs
USB_RN and USB_RP.
Port A mode: This pin can also be configured as the PA6 I/O.
19.11.8 USB_D+ and USB_D-
USB_D+ and USB_D- are the on-chip USB interface transceiver signals. When these
signals are enabled, the USB module uses them to communicate to an external USB bus.
When not used, each signal should be pulled to VDD using a 4.7-KΩ resistor.
19.11.9 USB_CLK
USB_CLK is used to connect an external 48-MHz oscillator to the USB module. When this
pin is tied to GND or VDD, the USB module automatically uses the internal CPU clock. In
this case the CLKIN must be 48 MHz if the system is to use the USB function.
19.11.10 INT1/USB Wake-on-Ring (USB_WOR)
The USB module allows for INT1 to generate the USB wake-on-ring signal to the USB host
controller. This function is enabled by a control bit in the USB module. WOR is provided
to allow the CPU and the USB interface to be woken up when in power down mode. This
occurs when the USB controller detects a resume state at the USB inputs.
The interrupt output of an ISDN transceiver, such as the MC145574, can be connected to
INT1/USB_WOR. Before putting the device into sleep mode, the USB module’s wake on
ring function can be enabled, the INT1 interrupt can be disabled, and USB power-down
modes can be enabled along with its interrupt. Then when the ISDN transceiver is activated,
its interrupt request can generate the USB wake on ring signal, which causes the host
controller on the PC to initiate USB traffic to the device. This in turn causes the USB
module to wake up the CPU. Note that USB_WOR, when configured by setting
USBEPCTL0[WOR_EN], is level-sensitive.
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MCF5272 User’s Manual
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