Functional Description
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
5.19.10.1.2 IN Transactions
An IN transaction receives data from 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 reset
The sequence of the transaction is:
1. Software sets the appropriate values in the following bits:
— USB_ADDRESS_CNF
— USB_ENDPOINT_CNF
— TOKEN_PID_CNT[7:0]
— DATA_LEN_CNT
— WRITE_READ#_CNT: (Note: This will always be 0 for IN transactions.)
— GO_CNT: (Note: This will always be 1 to initiate the transaction.)
Datasheet
211
INTEL [ INTEL ]
