Atmel SAM4S-XPLD Atmel ATSAM4S-XPLD ATSAM4S-XPLD Hoja De Datos

 934

SAM4S [DATASHEET]

11100E–ATARM–24-Jul-13

Data IN transactions are used in control, isochronous, bulk and interrupt transfers and conduct the transfer of data from
the device to the host. Data IN transactions in isochronous transfer must be done using endpoints with ping-pong
attributes.

To perform a Data IN transaction using a non ping-pong endpoint:

1.

The application checks if it is possible to write in the FIFO by polling TXPKTRDY in the endpoint’s UDP_CSRx reg-
ister (TXPKTRDY must be cleared).

2.

The application writes the first packet of data to be sent in the endpoint’s FIFO, writing zero or more byte values in 
the endpoint’s UDP_FDRx register,

3.

The application notifies the USB peripheral it has finished by setting the TXPKTRDY in the endpoint’s UDP_CSRx 
register.

4.

The application is notified that the endpoint’s FIFO has been released by the USB device when TXCOMP in the 
endpoint’s UDP_CSRx register has been set. Then an interrupt for the corresponding endpoint is pending while 
TXCOMP is set.

5.

The microcontroller writes the second packet of data to be sent in the endpoint’s FIFO, writing zero or more byte 
values in the endpoint’s UDP_FDRx register,

6.

The microcontroller notifies the USB peripheral it has finished by setting the TXPKTRDY in the endpoint’s 
UDP_CSRx register.

7.

The application clears the TXCOMP in the endpoint’s UDP_CSRx.

After the last packet has been sent, the application must clear TXCOMP once this has been set. 

TXCOMP is set by the USB device when it has received an ACK PID signal for the Data IN packet. An interrupt is
pending while TXCOMP is set. 

Warning: TX_COMP must be cleared after TX_PKTRDY has been set.

Note:

Refer to Chapter 8 of the Universal Serial Bus Specification, Rev 2.0, for more information on the Data IN proto-
col layer.

RX_Data_BKO
(UDP_CSRx)

ACK
PID

Data OUT

Data OUT
PID

NAK
PID

ACK
PID

Data Setup

Setup
PID

USB
Bus Packets

RXSETUP Flag

Set by USB Device

Cleared by Firmware

Set by USB
Device Peripheral

FIFO (DPR)
Content

Data Setup

Data

XX

XX

OUT

Interrupt Pending

Setup Received

Setup Handled by Firmware

Data Out Received

Data OUT

Data OUT

PID