Datasheet

Universal Serial Bus Module (USB)
Technical Data MC68HC908JB8•MC68HC08JB8•MC68HC08JT8 — Rev. 2.3
126 Universal Serial Bus Module (USB) Freescale Semiconductor
Each USB transaction is comprised of a series of packets. The USB
module supports the packet types shown in Figure 9-4. Token packets
are generated by the USB host and decoded by the USB device. Data
and handshake packets are both decoded and generated by the USB
device, depending on the type of transaction.
Figure 9-4. Supported USB Packet Types
The following sections detail each segment used to form a complete
USB transaction.
9.5.1.1 Sync Pattern
The NRZI bit pattern shown in Figure 9-5 is used as a synchronization
pattern and is prefixed to each packet. This pattern is equivalent to a
data pattern of seven 0s followed by a 1 ($80).
Figure 9-5. Sync Pattern
Token Packet:
IN
OUT SYNC PID PID
ADDR ENDP CRC5 EOP
SETUP
Data Packet:
DATA0 SYNC PID PID
DATA CRC16 EOP
DATA1 0 – 8 Bytes
Handshake Packet:
ACK
NAK SYNC PID PID
EOP
STALL
SYNC PATTERN
PID0 PID1Idle
NRZI Data
Encoding