UM0463

The USB state machine of the control endpoint

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The USB state machine of the control endpoint

3.1

The states

The USB state machine implemented in the library is used to handle the requests on the

control endpoint only. The state machine does not process any transactions of noncontrol

endpoints.

The USB state machine is designed to execute the SETUP requests. A SETUP request

consists of three stages: SETUP stage, data stage and status stage. The states of the state

machine are designed to match these three stages.

Figure 1.

States evaluation

Table 4.

States of USB state machine

State

Meaning

Wait_Setup

The state machine is in idle.

In_Data

The state machine is in data IN stage and is waiting for an IN data packet.

Out_Data

The state machine is in data OUT stage and is waiting to send an OUT data packet.

One_More_In

The state machine is in data IN stage and is waiting for a zero-length IN data packet when the

length of the data stream in the data stage is multiple of the maximum packet size of the

endpoint.

One_More_Out

The state machine is in data OUT stage and is waiting for sending a zero-length OUT data

packet when the length of the data stream in the data stage is a multiple of the maximum packet

size of the endpoint.

Wait_Status_In

The state machine is waiting for a status IN stage after the data OUT stage is finished, or after

the SETUP stage if there is no data stage.

Wait_Status_Out The state machine is waiting for a status OUT stage after the data IN stage is finished.

Address2Set

This is a special state to identify the process of a Set Address request.

State_Error

An error is detected, such as an invalid request.

SETUP

SETUP

SETUP

IN

OUT

IN

OUT

OUT

OUT

IN

IN

IN

Wait_Setup

In_Data

Wait_Status_In

Wait_Setup

Wait_Setup

Out_Data

Wait_Status_Out

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