NRF52820-QDAA-R datasheet(381/437 Pages) NORDIC

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Peripherals

If incoming data is corrupted (CRC does not match), the USBD controller automatically prevents DATA0/

DATA1 from toggling, to request the host to resend the data.

In some specific cases, the software may want to force a data toggle (usually reset) on a specific IN

endpoint, or force the expected toggle on an OUT endpoint, for instance as a consequence of the host

issuing

ClearFeature, SetInterface, or selecting an alternate setting. Controlling the data toggle

of data IN or OUT endpoint n (n=1..7) is done through register DTOGGLE.

The bulk/interrupt transaction in USB full-speed can be of any size up to 64 bytes. It must be a multiple of

four bytes and 32-bit aligned in memory.

When the USB transaction has completed, an EPDATA event is generated. Until new data has been

transferred by EasyDMA from memory to the USBD peripheral (signalled by the ENDEPIN[n] event), the

hardware will automatically respond with NAK to all incoming IN tokens. Software has to configure and

start the EasyDMA transfer once it is ready to send more data.

Each IN or OUT data endpoint has to be explicitly enabled by software through register EPINEN or

EPOUTEN, according to the configuration declared by the device and selected by the host through the

SetConfig command.

A disabled data endpoint will not respond to any traffic from the host. An enabled data endpoint will

normally respond NAK or ACK (depending on the readiness of the buffers), or STALL (if configured in

can be read back from register HALTED.EPIN[n] or HALTED.EPOUT[n]. The format of the returned 16-bit

value can be copied as is, as a response to a

GetStatusEndpoint request from the host.

Enabling or disabling an endpoint will not change its halted state. However, a USB reset will disable and

clear the halted state of all data endpoints.

The control endpoint 0 IN and OUT can also be enabled and/or halted using the same mechanisms, but

due to USB specification, receiving a SETUP will override its state.

6.26.10.1 Bulk and interrupt IN transaction

The host issues IN tokens to receive bulk/interrupt data. In order to send data, the software has to enable

the endpoint and prepare an EasyDMA transfer on the desired endpoint.

Bulk/interrupt IN endpoints are enabled or disabled through their respective INn bit (n=1..7) in EPINEN

It is also possible to stall or resume communication on an endpoint through the EPSTALL register.

USB host

USB device

DATA (0)

ACK

NAK

Events & tasks

Software

Figure 143: Bulk/interrupt IN transaction

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NRF52820-QDAA-R Datasheet(PDF) 381 Page - Nordic Semiconductor