This chapter introduces some key USB concepts and terminology that should make read-
ing the rest of this Technical Reference Manual easier.
1.2
EZ-USB Block Diagrams
+5V
Program &
Data
RAM
D+
D-
bytes
bytes
Serial
Interface
Engine
(SIE)
USB
Interface
IO Ports
GND
General
Purpose
Microprocessor
USB
Connector
USB
Transceiver
EZ-USB
Figure 1-1. AN2131S (44 pin) Simplified Block Diagram
The Cypress Semiconductor EZ-USB chip packs the intelligence required by a USB
peripheral interface into a compact integrated circuit. As Figure 1-1 illustrates, an inte-
grated USB transceiver connects to the USB bus pins D+ and D-. A Serial Interface
Engine (SIE) decodes and encodes the serial data and performs error correction, bit stuff-
ing, and other signaling-level details required by USB, and ultimately transfers data bytes
to and from the USB interface.
The internal microprocessor is enhanced 8051 with fast execution time and added fea-
tures. It uses internal RAM for program and data storage, making the EZ-USB family a
soft solution. The USB host downloads 8051 program code and device personality into
RAM over the USB bus, and then the EZ-USB chip re-connects as the custom device as
defined by the loaded code.
The EZ-USB family uses an enhanced SIE/USB interface (called the “USB Core”) which
has the intelligence to function as a full USB device even before the 8051. The enhanced
core simplifies 8051 code by implementing much of the USB protocol itself.
EZ-USB chips operate at 3.3V. This simplifies the design of bus-powered USB devices,
since the 5V power available in the USB connector (which the USB specification allows
to be as low as 4.4V) can drive a 3.3V regulator to deliver clean isolated power to the EZ-
USB chip.
Page 1-2
Chapter 1. Introducing EZ-USB
EZ-USB TRM v1.9
CYPRESS [ CYPRESS ]
