Usb Connection; Usb Protocol - Motorola M68HC08 Designer Reference Manual

3.2.2 USB Connection

3.2.3 USB Protocol

High Data Rate Wireless USB Optical Mouse Solution
MOTOROLA
Freescale Semiconductor, Inc.
The USB devices are connected to the host by a 4-wire cable. The USB signals
are transmitted over two wires (D+ and D–) on each point-to-point segment.
The cable also carries V
to devices. The USB data lines are required by the USB specification to have
an output voltage between 2.8 V and 3.6 V. The data lines also are required to
Ω
have an external 1.5-k
voltage source between 3.0 V and 3.6 V.
electrical connection for the voltage regulator.
4.0 V–5.5 V
3.3-V
REGULATOR
D+
LOW-SPEED
TRANSCEIVER
D–
For detailed electrical specifications, please refer to Universal Serial Bus
Specification Revision 2.0 at:
http://www.usb.org/developers/docs
The USB is a polled bus and the physical layers are configured in a tiered star
topology with point-to-point connections between the host and a hub or a
device. All data transfers are initiated and controlled by the host on a scheduled
basis. Each transaction is comprised of up to three packets.
the USB packet types.
The host will send out a token packet describing the type and direction of
transaction, device address, and endpoint number. The target device will
respond to the token if the address field decoding is a match. The transaction
direction is indicated in the token packet. The source of the transaction sends
a data packet, or indicates there is no information to transfer, and the
destination will respond with a handshake packet indicating if the transaction is
correct or not.
Universal Serial Bus (USB) Overview
For More Information On This Product,
Go to: www.freescale.com
Universal Serial Bus (USB) Overview
and GND wires (+5 V and ground) to deliver power
BUS
pullup resistor connected between a data line and a
Figure 3-2
USB DATA LINES
R1
USB CABLE
R1 = 1.5 kΩ ± 5%
R2 = 15 kΩ ± 5%
Figure 3-2. USB Connection
JB12 USB Module
shows the worst-case
HOST
OR
HUB
R2
R2
Figure 3-3 shows
DRM055
17