For purposes of downloading 8051 code, the Default USB Device requires only CON-
TROL endpoint zero. Nevertheless, the USB default machine is enhanced to support
other endpoints as shown in Figure 5-1 (note the alternate settings 1 and 2). This enhance-
ment is provided to allow the developer to get a head start generating USB traffic and
learning the USB system. All the descriptors are automatically handled by the EZ-USB
core, so the developer can immediately start writing code to transfer data over USB using
these pre-configured endpoints.
When the EZ-USB core establishes the Default USB Device, it also sets the proper end-
point configuration bits to match the descriptor data supplied by the EZ-USB core. For
example, bulk endpoints 2, 4, and 6 are implemented in the Default USB Device, so the
EZ-USB core sets the corresponding EPVAL bits. Chapter 6, “EZ-Bulk Transfers” con-
tains a detailed explanation of the EPVAL bits.
Tables 5-9 through 5-13 show the various descriptors returned to the host by the EZ-USB
core when ReNum=0. These tables describe the USB endpoints defined in Table 5-1,
along with other USB details, and should be useful to help understand the structure of
USB descriptors.
EZ-USB TRM v1.9
Chapter 5. EZ-USB CPU
Page 5-3
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