UM0463

Overview

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1

Overview

1.1

Functionality of the library

As a generic USB library, it provides the following functionalities:

●

Initialize the USB hardware cell

●

Answer all standard USB requests defined in Chapter 9 of USB specification [1]

●

Enumerate the USB device to the host with less user code intervention

●

Means for plug-in user code to handle nonstandard USB requests

●

Functions for sending and/or receiving data on all the endpoints

●

Optional DFU functionality without any user code intervention

1.2

Background of ST7 full-speed USB device

1.2.1

USB device

The ST7 full-speed USB device implements several USB endpoints. The number of

endpoints varies among products. Table 1 lists the endpoint configuration of each product:

The figures in the above table represent the maximum packet size allowed for a particular

endpoint. An endpoint is identified with its address and its direction. The endpoint in address

0 is the control endpoint and is always bidirectional. In the table, IN identifies that the

direction of the endpoint is from the device to the host and OUT identifies that the direction

of the endpoint is from the host to the device.

The data exchange on endpoints is done through endpoint DMA buffers. The endpoint DMA

buffers are located in the fixed location of RAM area and their locations vary among

products.

There is a pair of registers corresponding to each endpoint. They are the endpoint status

register and the DMA counter register. The endpoint status register identifies four status of

the endpoint:

Table 1.

Endpoint configuration

Endpoint

0

1 IN

1 OUT

2 IN

2 OUT

3 IN

4 IN

5 IN

ST7265

16

16

16

64

64

N/A

N/A

N/A

ST7SCR

88

N/A

64

64

888

Table 2.

Endpoint status

Status

Meaning

DISABLE

The endpoint does not answer any bus traffic.

STALL

The endpoint stalls any IN token for IN direction or OUT token for OUT direction.