#[repr(u8)]pub enum STATRXR {
Disabled = 0,
Stall = 1,
Nak = 2,
Valid = 3,
}Expand description
Status bits, for reception transfers Device mode These bits contain information about the endpoint status, which are listed in Reception status encoding on page2000.These bits can be toggled by software to initialize their value. When the application software writes ’0, the value remains unchanged, while writing ’1 makes the bit value toggle. Hardware sets the STRX bits to NAK when a correct transfer has occurred (VTRX=1) corresponding to a OUT or SETUP (control only) transaction addressed to this endpoint, so the software has the time to elaborate the received data before it acknowledge a new transaction Double-buffered bulk endpoints implement a special transaction flow control, which control the status based upon buffer availability condition (Refer to endpoints). If the endpoint is defined as Isochronous, its status can be only ‘VALID’ or ‘DISABLED’, so that the hardware cannot change the status of the endpoint after a successful transaction. If the software sets the STRX bits to ‘STALL’ or ‘NAK’ for an Isochronous endpoint, the USB peripheral behavior is not defined. These bits are read/write but they can be only toggled by writing ’1. Host mode These bits are the host application controls to start, retry, or abort host transactions driven by the channel. These bits also contain information about the device answer to the last IN channel transaction and report the current status of the channel according to the following STRX table of states: - DISABLE DISABLE value is reported in case of ACK acknowledge is received on a single-buffer channel. When in DISABLE state the channel is unused or not active waiting for application to restart it by writing VALID. Application can reset a VALID channel to DISABLE to abort a transaction. In this case the transaction is immediately removed from the Host execution list. If the aborted transaction was already under execution it will be regularly terminated on the USB but the relative VTRX interrupt is not generated. - VALID An Host channel is actively trying to submit USB transaction to device only when in VALID state.VALID state can be set by software or automatically by hardware on a NAKED channel at the start of a new frame. When set to VALID, an host channel enters the host execution queue and waits permission from the Host Frame Schedure to submit its configured transaction. VALID value is also reported in case of ACK acknowledge is received on a double-buffered channel. In this case the channel remains active on the alternate buffer while application needs to read the current buffer and toggle DTOGTX. In case software is late in reading and the alternate buffer is not ready, the host channel is automatically suspended transparently to the application. The suspended double buffered channel will be re-activated as soon as delay is recovered and DTOGTX is toggled. - NAK NAK value is reported in case of NAK acknowledge received. When in NAK state the channel is suspended and does not try to transmit. NAK state is moved to VALID by hardware at the start of the next frame, or software can change it to immediately retry transmission by writing it to VALID, or can disable it and abort the transaction by writing DISABLE - STALL STALL value is reported in case of STALL acknowledge received. When in STALL state the channel behaves as disabled. Application should not retry transmission but reset the USB and re-enumerate.
Value on reset: 0
Variants§
Disabled = 0
0: All reception requests addressed to this endpoint/channel are ignored.
Stall = 1
1: Device mode: the endpoint is stalled and all reception requests result in a STALL handshake. Host mode: this indicates that the device has STALLed the channel.
Nak = 2
2: Device mode: the endpoint is NAKed and all reception requests result in a NAK handshake. Host mode: this indicates that the device has NAKed the reception request.
Valid = 3
3: This endpoint/channel is enabled for reception.