MC908JB16DWE Datasheet, PDF (181/332 Pages) Freescale Semiconductor, Inc – Microcontrollers

Universal Serial Bus Module (USB)
11.7.3 USB Control Logic
The USB control logic manages data movement between the CPU and
the transceiver. The control logic handles both transmit and receive
operations on the USB. It contains the logic used to manipulate the
transceiver and the endpoint registers.
The byte count buffer is loaded with the active transmit endpoints byte
count value during transmit operations. This same buffer is used for
receive transactions to count the number of bytes received and, upon
the end of the transaction, transfer that number to the receive endpoints
byte count register.
When transmitting, the control logic handles parallel-to-serial
conversion, CRC generation, NRZI encoding, and bit stuffing.
When receiving, the control logic handles sync detection, packet
identification, end-of-packet detection, bit (un)stuffing, NRZI decoding,
CRC validation, and serial-to-parallel conversion. Errors detected by the
control logic include bad CRC, timeout while waiting for EOP, and bit
stuffing violations.
11.8 I/O Registers
These I/O registers control and monitor USB operation:
• USB address register (UADDR)
• USB control registers 0–4 (UCR0–UCR4)
• USB status registers 0–1 (USR0–USR1)
• USB interrupt registers 0–2 (UIR0–UIR2)
• USB endpoint 0 data registers 0–7 (UE0D0–UE0D7)
• USB endpoint 1 data registers 0–7 (UE1D0–UE1D7)
• USB endpoint 2 data registers 0–7 (UE2D0–UE2D7)
MC68HC908JB16 — Rev. 1.1
Freescale Semiconductor
Universal Serial Bus Module (USB)
Technical Data
181