Atmel ARM-Based Evaluation Kit for SAM4S16C, 32-Bit ARM® Cortex® Microcontroller ATSAM4S-WPIR-RD ATSAM4S-WPIR-RD Data Sheet
Product codes
ATSAM4S-WPIR-RD
1011
SAM4S Series [DATASHEET]
Atmel-11100G-ATARM-SAM4S-Datasheet_27-May-14
Figure 40-8.
Data IN Transfer for Ping-pong Endpoint
Warning:
There is software critical path due to the fact that once the second bank is filled, the driver has to wait for
TX_COMP to set TX_PKTRDY. If the delay between receiving TX_COMP is set and TX_PKTRDY is set too long,
some Data IN packets may be NACKed, reducing the bandwidth.
Warning:
Warning:
TX_COMP must be cleared after TX_PKTRDY has been set.
40.6.2.3 Data OUT Transaction
Data OUT transactions are used in control, isochronous, bulk and interrupt transfers and conduct the transfer of
data from the host to the device. Data OUT transactions in isochronous transfers must be done using endpoints
with ping-pong attributes.
Data OUT Transaction Without Ping-pong Attributes
To perform a Data OUT transaction, using a non ping-pong endpoint:
1. The host generates a Data OUT packet.
2. This packet is received by the USB device endpoint. While the FIFO associated to this endpoint is being
used by the microcontroller, a NAK PID is returned to the host. Once the FIFO is available, data are written
to the FIFO by the USB device and an ACK is automatically carried out to the host.
3. The microcontroller is notified that the USB device has received a data payload polling RX_DATA_BK0 in the
endpoint’s UDP_CSRx. An interrupt is pending for this endpoint while RX_DATA_BK0 is set.
4. The number of bytes available in the FIFO is made available by reading RXBYTECNT in the endpoint’s
UDP_CSRx.
5. The microcontroller carries out data received from the endpoint’s memory to its memory. Data received is
available by reading the endpoint’s UDP_FDRx.
6. The microcontroller notifies the USB device that it has finished the transfer by clearing RX_DATA_BK0 in the
endpoint’s UDP_CSRx.
7. A new Data OUT packet can be accepted by the USB device.
Data IN
Data IN
Read by USB Device
Read by USB Device
Bank 1
Bank 0
FIFO (DPR)
TXCOMP Flag
(UDP_CSRx)
(UDP_CSRx)
Interrupt Cleared by Firmware
Set by USB
Device
Device
TXPKTRDY Flag
(UDP_MCSRx)
(UDP_MCSRx)
ACK
PID
Data IN
PID
ACK
PID
Set by Firmware,
Data Payload Written in FIFO Bank 1
Data Payload Written in FIFO Bank 1
Cleared by USB Device,
Data Payload Fully Transmitted
Data Payload Fully Transmitted
Data IN
PID
USB Bus
Packets
Packets
Set by USB Device
Set by Firmware,
Data Payload Written in FIFO Bank 0
Data Payload Written in FIFO Bank 0
Written by
FIFO (DPR)
Microcontroller
Written by
Microcontroller
Written by
Microcontroller
Microcontroller
Load Data IN Bank 0
Load Data IN Bank 0
Microcontroller Load Data IN Bank 1
USB Device Send Bank 0
USB Device Send Bank 0
Microcontroller Load Data IN Bank 0
USB Device Send Bank 1
USB Device Send Bank 1
Interrupt Pending