Flexible for Many Applications
The EZ-USB architecture includes features that give the designer many options for creating an efficient and effective design that is tailored to the needs of an application.
Options for Loading 8051 Firmware
The EZ-USB family provides the peripheral developer with four options for loading its 8051 firmware.
Software file from the host system
Loading from a software file provides the maximum flex- ibility to the peripheral manu- facturer. This configuration takes advantage of the internal 4K or 8K RAM to load 8051 code and data from the host system. Because of the ReNumeration capability of EZ-USB chips, a new set of descriptors can be loaded after the initial enumera- tion without physically discon- necting the device. This allows device descriptors and 8051 program code to be loaded from a driver disk. Only the vendor ID, product ID, and device ID need to be loaded during boot time in hardware through a 16- byte EEPROM. Using this
configuration, users can implement a USB function in a tiny 44 PQFP package yielding a complete USB solution in less than one square inch of PC board space.
EEPROM loaded through the I2C port
The EZ-USB architecture supports an external EEPROM load through the I2C bus. This gives designers the capability to load 8051 program code from hard- ware. Because of the flexibility of the external EEPROM and inter- nal RAM, manufacturers have the option to make last-minute changes to a design/code without impacting production schedules.
External memory through the memory expansion port External memory may be added to EZ-USB family members in the 80-pin PQFP package. This memory is available through a memory expansion port. Separate 16-bit address and 8-bit data busses are also available to directly attach to a 64K EPROM, SRAM, or Flash memory. Unlike a standard 8051, the address and memory ports are not multi-
Loading 8051 Firmware from the Host
plexed, eliminating the need for glue logic for connection to external memory.
Internal ROM for peripheral manufacturers who migrate to the ROM-based EZ-USB chip EZ-USB ROM options are soft- ware and pin compatible to RAM members of the family. Therefore, high-volume customers can move easily to ROM when their 8051 firmware code is solidified.
