Peripheral Control Module

Figure 11-21. Control Transaction Formats

Action

Token Packet

Data Packet

Handshake Packet

UDC successfully received control from host

UDC temporarily unable to receive data

UDC endpoint needs host intervention

UDC detected PID, CRC, or bit stuff error

SETUP

DATA0

ACK

 

 

 

 

 

 

SETUP

DATA0

NAK

 

 

 

 

 

 

SETUP

DATA0

STALL

 

 

 

 

 

 

SETUP

DATA0

None

 

 

 

Packets from UDC to host are boldface

Control transfers are assembled by the host by first sending a control transaction to tell the UDC what type of control transfer is taking place (control read or control write), followed by two or more bulk data transactions. The control transaction, by default, uses a DATA0 transfer, and each subsequent bulk data transaction toggles between DATA1 and DATA0 transfers. For a control write to an endpoint, OUT transactions are used. For control reads, IN transactions are used. The transfer direction of the last bulk data transaction is reversed. It is used to report status and functions as a handshake. The last bulk data transaction always uses a DATA1 transfer by default (even if the previous bulk transaction used DATA1). For a control write, the last transaction is an IN from the UDC to the host, and for a control read, the last transaction is an OUT from the host to the UDC.

11.8.1.6UDC Device Requests

The UDC’s control, status, and data registers are used only to control and monitor the transmit and receive FIFOs for endpoints 1 and 2. All other UDC configuration and status reporting is controlled by the host via the USB bus using device requests that are sent as control transactions to endpoint

0.Each setup packet to endpoint 0 is 8 bytes long and specifies:

Data transfer direction: host to device, device to host

Data transfer type: standard, class, vendor

Data recipient: device, interface, endpoint, other

Number of bytes to transfer

Index or offset

Value: used to pass a variable-sized data parameter

Device request

11-62

SA-1100 Developer’s Manual

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Intel SA-1100 manual UDC Device Requests, Action Token Packet Data Packet, Setup DATA0, 11-62