Intel 6 SERIES CHIPSET - DATASHEET 01-2011 Datasheet page 209

Functional Description
5.18.9.1.1 OUT Transactions
An Out transaction sends data to the debug device. It can occur only when the
following are true:
• The debug port is enabled
• The debug software sets the GO_CNT bit
• The WRITE_READ#_CNT bit is set
The sequence of the transaction is:
1. Software sets the appropriate values in the following bits:
— USB_ADDRESS_CNF
— USB_ENDPOINT_CNF
— DATA_BUFFER[63:0]
— TOKEN_PID_CNT[7:0]
— SEND_PID_CNT[15:8]
— DATA_LEN_CNT
— WRITE_READ#_CNT: (note: this will always be 1 for OUT transactions)
— GO_CNT: (note: this will always be 1 to initiate the transaction)
2. The debug port controller sends a token packet consisting of:
— SYNC
— TOKEN_PID_CNT field
— USB_ADDRESS_CNT field
— USB_ENDPOINT_CNT field
— 5-bit CRC field
3. After sending the token packet, the debug port controller sends a data packet
consisting of:
— SYNC
— SEND_PID_CNT field
— The number of data bytes indicated in DATA_LEN_CNT from the DATA_BUFFER
— 16-bit CRC
NOTE: A DATA_LEN_CNT value of 0 is valid in which case no data bytes would be
included in the packet.
4. After sending the data packet, the controller waits for a handshake response from
the debug device.
— If a handshake is received, the debug port controller:
a. Places the received PID in the RECEIVED_PID_STS field
b. Resets the ERROR_GOOD#_STS bit
c. Sets the DONE_STS bit
— If no handshake PID is received, the debug port controller:
a. Sets the EXCEPTION_STS field to 001b
b. Sets the ERROR_GOOD#_STS bit
c. Sets the DONE_STS bit
Datasheet 209