Automatically Handles Low-Level USB Overhead

Automatically Handles Low-Level USB Overhead

A USB hardware connection is simpler than current interface standards (ISA, PCI, serial, parallel, and SCSI). For example, there are no IRQs or DMAs to set. USB does not use direct connections like RS232 or EPP (Enhanced Parallel Port). Instead, USB is a packetized protocol similar to telecommunication standards such as X.25 or frame relay. This makes software development complex.

The EZ-USB chip family reduces the complexity of USB. It has a predefined default descriptor that causes it to function as a generic USB device. Very little code is required to operate the EZ-USB chip when configured in this default state. The default descriptor can be replaced as the peripheral manufacturer devel- ops customized firmware.

Four Major Benefits of Smart USB Core

1The firmware code is smaller and more efficient than alternate

USB solutions. In the EZ-USB family, the memory requirement is reduced by a factor of two to five times as compared to other solutions. And, since less memory is needed for firmware, board size and system cost are reduced.

2USB firmware develop- ment is faster since there is less code to write. This

reduction in firmware allows the design team to concentrate more on software development for the peripheral function.

3Fewer 8051 MIPs are dedicated to USB processing. With the

EZ-USB family, as little as 10% of 8051 processing time is dedicated to USB. That makes 90% of the enhanced 8051 core’s processing time available for peripheral functions. Alternate solutions dedicate more of their micro- controller bandwidth to USB processing.

4The EZ-USB family handles most low-level USB overhead automati-

cally. Therefore, the learning curve to understand all the nuances of USB is reduced, yielding fewer code errors and faster product development.

Efficient EZ-USB Code

Firmware	EZ-USB Family	Alternate Solutions
File Type	EZ-USB Family	Alternate Solutions
File Type

Source	730 lines of C code	5445 lines of assembly code

Binary	< 1 Kbyte	> 5 Kbytes

Test Code Supports:

·USB Chapter 9

·String descriptors

·USB suspend/resume

·Remote wake-up

·Bulk endpoint loopback

EZ-USB Series 2100