AN2294 Freescale Semiconductor / Motorola, AN2294 Datasheet - Page 2

• Manufacturer Part Number: AN2294
• Description: MC68SZ328 USB Configuration Setup Application Note
• Manufacturer: Freescale Semiconductor / Motorola

Hardware Interface
1.1.2 Pipes
Pipes are abstract links between the host and the device. These links are not physical, instead, they are
software relationships. It is important to understand pipes relative to the types of data exchange and how
these exchanges take place between systems (host and device). There are two types of pipes, stream (used
in all transfers except control transfers) and message pipe (used in all control transfers).
1.1.3 Descriptors
Descriptors are structures of data sent by the device to the host for information purposes. With this data,
the host obtains all the required information necessary to connect to the peripheral device. This data is used
every time an enumeration occurs.
2 Hardware Interface
The MC68SZ328 processor has 3 main hardware interfaces: bus, transceiver, and USB crystal. This
section describes these interfaces.
2.1 Bus and Power Management
The bus is responsible for transferring the data between the host and the USB module. The USB bus is
comprised of four lines D+, D-, Vbus, and ground. The USB module can operate only as a self-powered
device with the power supplied by the DragonBall processor’s power pins, as the internal USB module
does not have separate power pins.
2.2 Transceiver
The following MC68SZ328 output pins are responsible for the interface with the USB transceiver:
Figure 1 on page 3, shows the connections between the DragonBall processor and transceiver ISP1105W
using the USB pin outputs. Note that the SPEED signal is driven high on this diagram. This is necessary
for running at full speed mode.
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USBD_VPO
USBD_SUSPND
USBD_VMO
USBD_ROEB
USBD_VM
USBD_VP
USBD_RCV
USBD_AFE
Freescale Semiconductor, Inc.
For More Information On This Product,
MC68SZ328 Application Note
Go to: www.freescale.com
MOTOROLA