Altera Cyclone V Device Handbook page 914

cv_54018
2013.12.30
USB Transactions
In device mode, the MAC decodes and checks the integrity of all token packets. For valid OUT or SETUP
tokens, the following DATA packet is also checked. If the data packet is valid, the MAC performs the following
steps:
1. Writes the data to the receive FIFO buffer
2. Sends the appropriate handshake when required to the USB host
If a receive FIFO buffer is not available, the MAC sends a NAK response to the host. The MAC also supports
ping protocol.
For IN tokens, if data is available in the transmit FIFO buffer, the MAC performs the following steps:
1. Reads the data from the FIFO buffer
2. Forms the data packet
3. Transmits the packet to the host
4. Receives the response from the host
5. Sends the updated status to the PFC
In host mode, the MAC receives a token request from the AIU. The MAC performs the following steps:
1. Builds the token packet
2. Sends the packet to the device
For OUT or SETUP transactions, the MAC also performs the following steps:
1. Reads the data from the transmit FIFO buffer
2. Assembles the data packet
3. Sends the packet to the device
4. Waits for a response
The response from the device causes the MAC to send a status update to the AIU.
For IN or PING transactions, the MAC waits for the data or handshake response from the device. For data
responses, the MAC performs the following steps:
1. Validates the data
2. Writes the data to the receive FIFO buffer
3. Sends a status update to the AIU
4. Sends a handshake to the device, if appropriate
Host Protocol
In host mode, the MAC performs the following functions:
• Detects connect, disconnect, and remote wakeup events on the USB link
• Initiates reset
• Initiates speed enumeration processes
• Generates Start of Frame (SOF) packets.
USB 2.0 OTG Controller
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USB Transactions
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