Datasheet

103
4341H–MP3–10/07
AT8xC51SND2C/MP3B
16. Universal Serial Bus
The AT8xC51SND2C implements a USB device controller supporting full speed data transfer. In
addition to the default control endpoint 0, it provides 2 other endpoints, which can be configured
in control, bulk, interrupt or isochronous modes:
• Endpoint 0: 32-Byte FIFO, default control endpoint
• Endpoint 1, 2: 64-Byte Ping-pong FIFO,
This allows the firmware to be developed conforming to most USB device classes, for example:
• USB Mass Storage Class Bulk-only Transport, Revision 1.0 - September 31, 1999
• USB Human Interface Device Class, Version 1.1 - April 7, 1999
• USB Device Firmware Upgrade Class, Revision 1.0 - May 13, 1999
16.1 USB Mass Storage Class Bulk-Only Transport
Within the Bulk-only framework, the Control endpoint is only used to transport class-specific and
standard USB requests for device set-up and configuration. One Bulk-out endpoint is used to
transport commands and data from the host to the device. One Bulk in endpoint is used to trans-
port status and data from the device to the host.
The following AT8xC51SND2C configuration adheres to those requirements:
• Endpoint 0: 32 Bytes, Control In-Out
• Endpoint 1: 64 Bytes, Bulk-in
• Endpoint 2: 64 Bytes, Bulk-out
16.2 USB Device Firmware Upgrade (DFU)
The USB Device Firmware Update (DFU) protocol can be used to upgrade the on-chip Flash
memory of the AT89C51SND2C. This allows installing product enhancements and patches to
devices that are already in the field. 2 different configurations and descriptor sets are used to
support DFU functions. The Run-Time configuration co-exist with the usual functions of the
device, which is USB Mass Storage for AT89C51SND2C. It is used to initiate DFU from the nor-
mal operating mode. The DFU configuration is used to perform the firmware update after device
re-configuration and USB reset. It excludes any other function. Only the default control pipe
(endpoint 0) is used to support DFU services in both configurations.
The only possible value for the MaxPacketSize in the DFU configuration is 32 Bytes, which is the
size of the FIFO implemented for endpoint 0.
16.3 Description
The USB device controller provides the hardware that the AT8xC51SND2C needs to interface a
USB link to a data flow stored in a double port memory.
It requires a 48 MHz reference clock provided by the clock controller as detailed in Section "",
page 104. This clock is used to generate a 12 MHz Full Speed bit clock from the received USB
differential data flow and to transmit data according to full speed USB device tolerance. Clock
recovery is done by a Digital Phase Locked Loop (DPLL) block.
The Serial Interface Engine (SIE) block performs NRZI encoding and decoding, bit stuffing, CRC
generation and checking, and the serial-parallel data conversion.
The Universal Function Interface (UFI) controls the interface between the data flow and the Dual
Port RAM, but also the interface with the C51 core itself.