Product Brief, Rev. 3
December 2001
USS-820D
USB Device Controller
Features
■Full compliance with the
Universal Serial Bus Specifi-
cation Revision 1.1
.
■Backward compatible with USS-820B and USS-820C
revisions.
■Self-powered or bus-powered USB device. Meets USB
power specifications for bus-powered devices.
■Full-speed USB device (12 Mbits/s).
■USB device controller with protocol control and admin-
istration for up to 16 USB endpoints.
■Supports control, interrupt, bulk, and isochronous
transfers for all 16 endpoints.
■Programmable endpoint types and FIFO sizes and
internal 1120-byte logical (2240-byte physical for dual-
packet mode) shared FIFO storage allow a wide vari-
ety of configurations.
■Dual-packet mode of FIFOs reduces latency.
■Supports USB remote wake-up feature.
■On-chip crystal oscillator allows external 12 MHz crys-
tal or 3 V/5 V clock source.
■On-chip analog PLL creates 48 MHz clock from inter-
nal 12 MHz clock.
■Integrated USB transceivers.
■5 V tolerant I/O buffers allow operation in 3 V or 5 V
system environment.
■Implemented in Agere Systems Inc. 0.25 µm, 3 V stan-
dard-cell library.
■44-pin MQFP (USS-820D).
■48-pin TQFP (USS-820TD).
■Evaluation kit available.
New Features After Revision B
■New, centralized FIFO status bits and interrupt output
pin reduce firmware load.
■New, additional nonisochronous transmit mode allows
NAK response to cause interrupt.
■Isochronous behavior enhancements simplify firmware
control.
■Additional FIFO sizes for nonisochronous endpoints.
■USB reset can be programmed to clear device
address.
■USB reset output status pin.
■Firmwareabilitytowakeupandresetasuspended
device.
■Lower power.
■5 V supply no longer required for 5 V tolerant opera-
tion.
Applications
■Suitable for peripherals with embedded microproces-
sors.
■Glueless interface to microprocessor buses.
■Support of multifunction USB implementations, such
as printer/scanner and integrated multimedia applica-
tions.
■Suitable for a broad range of device class peripherals
in the USB standard.
Description
USS-820D is a USB device controller that provides a
programmable bridge between the USB and a local
microprocessor bus. It is available in two package types:
44-pin MQFP (USS-820D) and 48-pin TQFP (USS-
820TD, formerly USS-825). The USS-820D allows PC
peripherals to upgrade to USBconnectivity without major
redesign effort. It is programmable through a simple
read/write register interface that is compatible with
industry-standard USB microcontrollers.
USS-820D is designed in 100% compliance with the USB
industry standard, allowing device-side USB products to
be reliably installed using low-cost, off-the-shelf cables
and connectors.
The integrated USB transceiver supports 12 Mbits/s full-
speed operation. FIFO options support all four transfer
types: control, interrupt, bulk, and isochronous, as
described in
Universal Serial Bus Specification Revision
1.1,
with a wide range of packet sizes. Its double sets of
FIFO enable the dual-packet mode feature. The dual-
packet mode feature reduces latency by allowing simulta-
neous transfers on the host and microprocessor sides of
a given unidirectional endpoint.