SAM3SD8B Atmel Corporation, SAM3SD8B Datasheet - Page 959

• Manufacturer Part Number: SAM3SD8B
• Manufacturer: Atmel Corporation

Figure 36-5. Control Read and Write Sequences
Notes:
36.6.2
36.6.2.1
11090A–ATARM–10-Feb-12
11090A–ATARM–10-Feb-12
1. During the Status IN stage, the host waits for a zero length packet (Data IN transaction with no data) from the device using
2. During the Status OUT stage, the host emits a zero length packet to the device (Data OUT transaction with no data).
Handling Transactions with USB V2.0 Device Peripheral
DATA1 PID. Refer to Chapter 8 of the Universal Serial Bus Specification, Rev. 2.0, for more information on the protocol layer.
Setup Transaction
Control Read
Control Write
No Data
Control
Setup is a special type of host-to-device transaction used during control transfers. Control trans-
fers must be performed using endpoints with no ping-pong attributes. A setup transaction needs
to be handled as soon as possible by the firmware. It is used to transmit requests from the host
to the device. These requests are then handled by the USB device and may require more argu-
ments. The arguments are sent to the device by a Data OUT transaction which follows the setup
transaction. These requests may also return data. The data is carried out to the host by the next
Data IN transaction which follows the setup transaction. A status transaction ends the control
transfer.
When a setup transfer is received by the USB endpoint:
Thus, firmware must detect the RXSETUP polling the UDP_CSRx or catching an interrupt, read
the setup packet in the FIFO, then clear the RXSETUP. RXSETUP cannot be cleared before the
setup packet has been read in the FIFO. Otherwise, the USB device would accept the next Data
OUT transfer and overwrite the setup packet in the FIFO.
• The USB device automatically acknowledges the setup packet
• RXSETUP is set in the UDP_CSRx register
• An endpoint interrupt is generated while the RXSETUP is not cleared. This interrupt is
carried out to the microcontroller if interrupts are enabled for this endpoint.
Setup Stage
Setup Stage
Setup Stage
Setup TX
Setup TX
Setup TX
Status Stage
Status IN TX
Data OUT TX
Data IN TX
Data Stage
Data Stage
Data OUT TX
Data IN TX
Status OUT TX
Status Stage
Status IN TX
Status Stage
SAM3S8/SD8
SAM3S8/SD8
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