Cypress CY3674, User Manual

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EZ-USB Development Kit User Guide, Doc. # 001-66390 Rev. *D 35
5. EZ-USB Firmware Frameworks
The firmware frameworks simplify and accelerate USB peripheral development using the EZ-USB
chip. The frameworks implement the 8051 code for EZ-USB chip initialization, USB standard device
request handling, and USB suspend power management services. The user provides a USB
descriptor table and code to implement the peripheral function to complete a fully compliant USB
device. The frameworks provide function hooks and example code to help with this process. The
frameworks use the EZ-USB library to carry out common functions and for EZ-USB register defini-
tions. Most of the firmware examples in the EZ-USB DVK are based on the frameworks.
5.1 Frameworks Overview
The frameworks implement the basic functionality required of a USB compliant peripheral device. By
linking a minimal descriptor table, it is possible to build a fully compliant Device Framework (USB
Specification, Chapter 9).
At startup, the frameworks initialize all its internal state variables. It then calls the user initialization
function TD_Init(). Upon return, the frameworks initialize the USB interface to the unconfigured state
and enable interrupts. The firmware then re-enumerates and starts the co-operative task dispatcher.
The task dispatcher repeatedly performs the following tasks in the given order.
1. Calls the user function TD_Poll().
2. Determines if a standard device request is pending. If so, it parses the received command and
responds accordingly. The frameworks automatically handle the standard USB requests, but
allow the user to override the default behavior for all requests.
3. Determines if the USB core has reported a USB suspend event. If so, it calls the user function
TD_Suspend().
EZ-USB interrupts are handled by the frameworks. It provides hooks for user code notification of
USB events.