Designer Reference Manual USB08 Evaluation Board
60 Universal Serial Bus (USB) Interface MOTOROLA
Universal Serial Bu s (USB) Interface
The USB specific a ti on(1) which can be found on the Wor ld Wide Web at:
http://www.usb.org
is an industry standard, which exactly defines this bus system beginning
with the electrical interface up to the higher protocol layers to guaran tee
the inter-operability of all the different devices. A simple way o f handli ng
is the most important requirement for USB devices from the view of the
user.
Several versions of the USB specification exist. Apart from the already
established release 1.1, on which the MC68HC908JB 8 and the available
reference design is based, the specification 2.0 was compiled in the year
2000 by the USB Implementers Forum (USB-IF). This version ensures
compatibility to the version 1.1 and contains the already known speed
classifications “low speed” and “full speed”. Beyond that, release 2.0
introduces a high-speed device type. First high-speed devices are
expected to be established in the market by end of the year 2001.
The basic specification of the USB is supplemented by several class
specifications for certain types of device classes, which can be found
frequently (for example, human interface device class for keyboards,
mouse pointers, etc.). Further information regarding conditions and
contents of basic and class specifications can be found on the World
Wide Web at:
http://www.usb.org
4.3 Characteristics of the USB08 Reference Design
The USB08 reference design shows, via a detailed example, how the
integrated USB module of the Motorola microcontroller unit (MCU)
MC68HC908JB8 can be used. The MCU is used for a measuring and
control application and exchanges data with a PC via the USB. This
reference design shows that communication to a PC using USB can be
just as simple as a normal RS232 link.
1. Universal Serial Bus Specification Revision 1.1; September 23, 1998