Another Use for the Default USB Device
The Default USB Device is established at power-on to set up a USB device capable of
downloading firmware into EZ-USB RAM. Another useful feature of the EZ-USB
default device is that 8051 code can be written to support the already-configured Generic
USB device. Before bringing the 8051 out of reset, the EZ-USB core enables certain
endpoints and reports them to the host via descriptors. By utilizing the USB default
machine (by keeping ReNum=0), the 8051 can, with very little code, perform meaningful
USB transfers that use these default endpoints. This accelerates the USB learning curve.
To see an example of how little code is actually necessary, take a look at Section 6.11,
"Polled Bulk Transfer Example."
5.2
The Default USB Device
The Default USB Device consists of a single USB configuration containing one interface
(interface 0) with three alternate settings 0, 1, and 2. The endpoints reported for this
device are shown in Table 5-1. Note that alternate setting zero uses no interrupt or isoch-
ronous bandwidth, as recommended by the USB Specification.
Table 5-1. EZ-USB Default Endpoints
Endpoint
Type
Alternate Setting
1
0
2
Maximum Packet Size (Bytes)
0
CTL
INT
64
0
0
0
0
0
0
0
0
0
0
0
0
0
64
16
64
64
64
64
64
64
16
16
16
16
16
16
64
64
64
64
64
64
64
64
256
256
16
16
16
16
1-IN
2-IN
BULK
BULK
BULK
BULK
BULK
BULK
ISO
2-OUT
4-IN
4-OUT
6-IN
6-OUT
8-IN
8-OUT
9-IN
ISO
ISO
9-OUT
10-IN
10 OUT
ISO
ISO
ISO
Page 5-2
Chapter 5. EZ-USB CPU
EZ-USB TRM v1.9
CYPRESS [ CYPRESS ]
