HCS08 datasheet(322/374 Pages) NXP

322 / 374 page

Universal Serial Bus Device Controller (S08USBV1)

MC9S08JM60 Series Data Sheet, Rev. 5

322

Freescale Semiconductor

a resume from low-power suspend. This will trigger an asynchronous interrupt to wake the CPU

from stop3 mode and resume clocks to the USB module.

NOTE

As a precaution, after LPRESF is set, firmware must check the state of the

USB bus to see if the K-state was a result of a transient event and not a true

host-initiated resume. If this is the case, then the device can drop back into

stop3 if necessary. To do this, the RESUME interrupt can be enabled in

conjunction with the USBRESMEN feature. Then, after LPRESF is set, and

a K-state is still detected approximately 2.5 µs after clocks have restarted,

firmware can check that the RESUMEF interrupt has triggered, indicating

resume signaling from the host.

17.4.6.2.2

USB Reset Signaling

Reset can wake a device from the suspend state.

17.4.6.2.3

Remote Wakeup

The USB device can send a resume event to the host by writing to the CRESUME bit. Firmware must first

set the bit for the time period required by the USB Specification Rev. 2.0 (Section 7.1.7.7) and then clear

it to 0.

17.4.7

Resets

The module supports multiple types of resets. The first is a bus reset generated by the USB Host, the

second is a module reset generated by the MCU.

17.4.7.1

USB Bus Reset

At any time, the USB host may issue a reset to one or all of the devices attached to the bus. A USB reset

is defined as a period of single ended zero (SE0) on the cable for greater than 2.5

μs. When the device

detects reset signaling, it resets itself to the unconfigured state, and sets its USB address zero. The USB

host uses reset signaling to force one or all connected devices into a known state prior to commencing

enumeration.

The USB module responds to reset signaling by asserting the USBRST interrupt in the INTSTAT register.

Software is required to service this interrupt to ensure correct operation of the USB.

17.4.7.2

USB Module Reset

USB module resets are initiated on-chip. During a module reset, the USB module is configured in the

default mode. The USB module can also be forced into its reset state by setting the USBRESET bit in the

USBCTL0 register. The default mode includes the following settings:

•

Interrupts masked.

•

USB clock enabled

•

USB voltage regulator disabled

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