Common use of Transfer Errors Clause in Contracts

Transfer Errors. Transfer errors for isochronous errors fall into four categories: ?? transmission ?? sequence ?? time ?? system 4.3.2.3.5.1 Transmission Errors Since there is no handshake for isochronous transfers, the Host Controller can detect transmission errors for transfers only from an endpoint to the host (IN). The error may be either a CRC error, a BITSTUFFING error, or a DEVICENOTRESPONDING error. If any of these errors occurs during the transfer, the ConditionCode of PacketStatusWord[R] is set accordingly and the size field reflects the number of bytes received (up to the size of the buffer defined for the frame) and placed in the memory buffer. For a bit stuffing error, the Host Controller writes up only to the last byte received before the bit stuffing error is detected. If a transmission error is detected along with a sequence or system error, the transmission error is the one that is reported in the ConditionCode . A PID check error in the PID from an endpoint is reported with a ConditionCode of PIDCHECKFAILURE. 4.3.2.3.5.2 Sequence Errors A sequence error occurs when the endpoint sends more or less data than is expected and a transmission error is not present. If the endpoint sends more data than will fit in the specified buffer, the ConditionCode for the PacketStatusWord is set to DATAOVERRUN and the size field is set to the size of the buffer. The Host Controller writes the received data to memory up to the limit of the buffer defined for the frame. If the endpoint sends less data than defined by the buffer, the ConditionCode for the PacketStatusWord is set to DATAUNDERRUN. 4.3.2.3.5.3 Time Errors Each packet has a specific frame in which it is to be transferred. It is possible that the Host Controller cannot start or complete the transfer in the specified frame. There are two manifestations of this type of error: skipped packets and late retirement of an Isochronous TD. Skipped packets occur if the Host Controller does not process an Isochronous TD in a frame for which the Isochronous TD has data. A skipped packet is indicated when an Offset/PacketStatusWord is set to NOT ACCESSED after the Isochronous TD is retired. This indicates that the Host Controller did not process the Isochronous TD for the frame and therefore did not change the Offset to a PacketStatusWord. When the Host Controller skips the last packet of the Isochronous TD, a more significant error occurs. Since the Isochronous TD was not processed in the frame in which it should have been retired, the Isochronous TD remains on its ED’s queue. When the Host Controller processes the Isochronous TD in a latter frame, it finds that the time for expiration of the Isochronous TD has passed. In such cases, the Host Controller sets the ConditionCode for the Isochronous TD to DATAOVERRUN and retires the Isochronous TD (it does not, however, set the Halted bit in the ED). The Host Controller then accesses the next Isochronous TD for the same ED and processes it. Note: Setting DATAOVERRUN in the ConditionCode for the Isochronous TD rather than the PacketStatusWord indicates a time overrun. The same code in a PacketStatusWord will indicate a true data buffer overrun. 0xFFFC 0xFFFE 0xFFFE (-2) 3 Do nothing 0xFFFD 0xFFFE 0xFFFF (-1) 3 Do nothing 0xFFFE 0xFFFE 0x0000 3 Send data packet 0 Host Controller does not process Isochronous TD for three frames due to schedule overrun, then... 0x0002 0xFFFE 0x0004 3 Retire Isochronous TD with DATAOVERRUN in ▇▇▇.▇▇

Transfer Errors. Transfer There are several types of transfer errors for isochronous errors that must be handled by the HC. They fall into four the following categories: ?? transmission ?? sequence ?? time ?? system 4.3.2.3.5.1 system Transmission Errors Since there is no handshake for isochronous transferserrors are errors that occur in communicating information over the USB wires and manifest themselves as CRC errors, BITSTUFFING errors, DEVICENOTRESPONDING errors. Sequence errors occur when the Host Controller can detect transmission errors for transfers only from an endpoint to the host (IN). The error may be either a CRC error, a BITSTUFFING error, or a DEVICENOTRESPONDING error. If any number of these errors occurs during the transfer, the ConditionCode of PacketStatusWord[R] is set accordingly and the size field reflects data bytes received does not match the number of bytes received (expected from an endpoint. System errors occur when the Host Controller has a problem resulting from the HC’s system environment that cannot otherwise be attributed to USB. 4.3.1.3.6.1 Transmission Errors For errors in this category, USB defines a policy that allows the transaction to be retried for up to three times before the size of transfer is failed and returned to the buffer defined for client. The Host Controller supports this policy with the frame) and placed in ErrorCount field. This field is initialized to 0 by the memory bufferHost Controller Driver when the General TD is queued. For a bit stuffing This field is updated after each transaction attempt. If there is no transmission error, the Host Controller writes up only field is written to the last byte received before the bit stuffing error 0. If, however, there is detected. If a transmission error is detected along with a sequence or system error, the field is incremented. If the ErrorCount field reaches 2 (10b) and another transmission error occurs (the third error in a row), the TD is retired to the one that Done Queue and the endpoint is reported in halted. Data toggle mismatches on input data are counted as transmission errors. The cause of a data toggle mismatch is either failure of the ConditionCode endpoint to receive an ACK or a broken device. A PID check Data received when the data toggle mismatches is discarded and never written to host memory. An error in the PID from an endpoint check field is counted as a transmission error and is reported with a ConditionCode of PIDCHECKFAILURE. 4.3.2.3.5.2 4.3.1.3.6.2 Sequence Errors Sequence errors occur only on reads from an endpoint to the Host Controller (IN). Sequence errors are not checked unless the data packet is received without a transmission error. There are two types of sequence errors: data overrun and data underrun. When either of these error conditions is encountered, the ConditionCode field is set accordingly, the General TD is retired, and the endpoint is halted. A sequence data overrun error occurs when the number of bytes received from an endpoint sends more exceeds either Maximum Packet Size or the number of bytes remaining in a General TD’s buffer. In the case of an overrun condition, the Host Controller writes to memory all of the data received up to the point where the data overrun condition was created. When the General TD is retired, CurrentBufferPointer points to the start of the data packet in error; however, all of the data bytes are valid and the data toggle will have advanced. The second type of sequence error, data underrun, occurs when the number of data bytes received from an endpoint is less data than allowed. Even though a General TD is expected and a transmission always retired when the number of bytes received from an endpoint is less than Maximum Packet Size, it does not always create an error is not presentcondition. If the amount of received data fills the buffer exactly (last byte of a data packet written to BufferEnd), then a normal completion condition exists regardless of the size of the data packet. The General TD is retired with a ConditionCode of NOERROR and the endpoint sends more is not halted. If the data than will fit in packet does not fill the specified bufferbuffer exactly, the bufferRounding bit determines how the General TD will be retired. If the bufferRounding bit is not set, then the underrun is treated as an error condition. The ConditionCode for the PacketStatusWord is set to DATAOVERRUN and the size field is set to DATAUNDERRUN, the size of General TD retired, and the buffer. The Host Controller writes the received data to memory up to the limit of the buffer defined for the frameendpoint is halted. If the endpoint sends less data than defined bufferRounding field is set, then the General TD is retired without error. This condition is differentiated from a buffer-filled completion condition by CurrentBufferPointer not being zero when the buffer, the ConditionCode for the PacketStatusWord General TD is set to DATAUNDERRUNretired. 4.3.2.3.5.3 Time 4.3.1.3.6.3 System Errors Each packet has For General TDs, system error sources are limited. In particular, an OpenHCI Host Controller will never have an overrun or underrun of its internal buffering for a specific frame in which it General TD. An OpenHCI Host Controller is not allowed to be transferred. It issue an IN to an endpoint unless there is possible that sufficient buffer space within the Host Controller cannot start or complete the transfer in the specified frame. There are two manifestations of this type of error: skipped packets and late retirement of an Isochronous TD. Skipped packets occur if the Host Controller does not process an Isochronous TD in to accept a frame for which the Isochronous TD has data. A skipped packet is indicated when an Offset/PacketStatusWord is set to NOT ACCESSED after the Isochronous TD is retired. This indicates that the Host Controller did not process the Isochronous TD for the frame and therefore did not change the Offset to a PacketStatusWord. When the Host Controller skips the last data packet of Maximum Packet Size from the Isochronous endpoint (64 bytes for a General TD, a more significant error occurs) without having to access system memory. Since the Isochronous TD was not processed in the frame in which it should have been retired, the Isochronous TD remains on its ED’s queue. When the Host Controller processes the Isochronous TD in a latter frame, it finds that the time for expiration of the Isochronous TD has passed. In such casesSimilarly, the Host Controller sets is not allowed to issue an OUT or SETUP token unless it has pre-fetched to an internal buffer all the ConditionCode for data that is sent to the Isochronous TD to DATAOVERRUN and retires the Isochronous TD (it does not, however, set the Halted bit endpoint in the ED). The Host Controller then accesses the next Isochronous TD for the same ED and processes it. Note: Setting DATAOVERRUN in the ConditionCode for the Isochronous TD rather than the PacketStatusWord indicates a time overrun. The same code in a PacketStatusWord will indicate a true data buffer overrun. 0xFFFC 0xFFFE 0xFFFE (-2) 3 Do nothing 0xFFFD 0xFFFE 0xFFFF (-1) 3 Do nothing 0xFFFE 0xFFFE 0x0000 3 Send data packet 0 Host Controller does not process Isochronous TD for three frames due to schedule overrun, then... 0x0002 0xFFFE 0x0004 3 Retire Isochronous TD with DATAOVERRUN in ▇▇▇phase.▇▇

Transfer Errors. Transfer There are several types of transfer errors for isochronous errors that must be handled by the HC. They fall into four the following categories: ?? • transmission ?? • sequence ?? time ?? system 4.3.2.3.5.1 • system Transmission Errors Since there is no handshake for isochronous transferserrors are errors that occur in communicating information over the USB wires and manifest themselves as CRC errors, BITSTUFFING errors, DEVICENOTRESPONDING errors. Sequence errors occur when the Host Controller can detect transmission errors for transfers only from an endpoint to the host (IN). The error may be either a CRC error, a BITSTUFFING error, or a DEVICENOTRESPONDING error. If any number of these errors occurs during the transfer, the ConditionCode of PacketStatusWord[R] is set accordingly and the size field reflects data bytes received does not match the number of bytes received (expected from an endpoint. System errors occur when the Host Controller has a problem resulting from the HC’s system environment that cannot otherwise be attributed to USB. 4.3.1.3.6.1 Transmission Errors For errors in this category, USB defines a policy that allows the transaction to be retried for up to three times before the size of transfer is failed and returned to the buffer defined for client. The Host Controller supports this policy with the frame) and placed in ErrorCount field. This field is initialized to 0 by the memory bufferHost Controller Driver when the General TD is queued. For a bit stuffing This field is updated after each transaction attempt. If there is no transmission error, the Host Controller writes up only field is written to the last byte received before the bit stuffing error 0. If, however, there is detected. If a transmission error is detected along with a sequence or system error, the field is incremented. If the ErrorCount field reaches 2 (10b) and another transmission error occurs (the third error in a row), the TD is retired to the one that Done Queue and the endpoint is reported in halted. Data toggle mismatches on input data are counted as transmission errors. The cause of a data toggle mismatch is either failure of the ConditionCode endpoint to receive an ACK or a broken device. A PID check Data received when the data toggle mismatches is discarded and never written to host memory. An error in the PID from an endpoint check field is counted as a transmission error and is reported with a ConditionCode of PIDCHECKFAILURE. 4.3.2.3.5.2 4.3.1.3.6.2 Sequence Errors Sequence errors occur only on reads from an endpoint to the Host Controller (IN). Sequence errors are not checked unless the data packet is received without a transmission error. There are two types of sequence errors: data overrun and data underrun. When either of these error conditions is encountered, the ConditionCode field is set accordingly, the General TD is retired, and the endpoint is halted. A sequence data overrun error occurs when the number of bytes received from an endpoint sends more exceeds either Maximum Packet Size or the number of bytes remaining in a General TD’s buffer. In the case of an overrun condition, the Host Controller writes to memory all of the data received up to the point where the data overrun condition was created. When the General TD is retired, CurrentBufferPointer points to the start of the data packet in error; however, all of the data bytes are valid and the data toggle will have advanced. The second type of sequence error, data underrun, occurs when the number of data bytes received from an endpoint is less data than allowed. Even though a General TD is expected and a transmission always retired when the number of bytes received from an endpoint is less than Maximum Packet Size, it does not always create an error is not presentcondition. If the amount of received data fills the buffer exactly (last byte of a data packet written to BufferEnd), then a normal completion condition exists regardless of the size of the data packet. The General TD is retired with a ConditionCode of NOERROR and the endpoint sends more is not halted. If the data than will fit in packet does not fill the specified bufferbuffer exactly, the bufferRounding bit determines how the General TD will be retired. If the bufferRounding bit is not set, then the underrun is treated as an error condition. The ConditionCode for the PacketStatusWord is set to DATAOVERRUN and the size field is set to DATAUNDERRUN, the size of General TD retired, and the buffer. The Host Controller writes the received data to memory up to the limit of the buffer defined for the frameendpoint is halted. If the endpoint sends less data than defined bufferRounding field is set, then the General TD is retired without error. This condition is differentiated from a buffer-filled completion condition by CurrentBufferPointer not being zero when the buffer, the ConditionCode for the PacketStatusWord General TD is set to DATAUNDERRUNretired. 4.3.2.3.5.3 Time 4.3.1.3.6.3 System Errors Each packet has For General TDs, system error sources are limited. In particular, an OpenHCI Host Controller will never have an overrun or underrun of its internal buffering for a specific frame in which it General TD. An OpenHCI Host Controller is not allowed to be transferred. It issue an IN to an endpoint unless there is possible that sufficient buffer space within the Host Controller cannot start or complete the transfer in the specified frame. There are two manifestations of this type of error: skipped packets and late retirement of an Isochronous TD. Skipped packets occur if the Host Controller does not process an Isochronous TD in to accept a frame for which the Isochronous TD has data. A skipped packet is indicated when an Offset/PacketStatusWord is set to NOT ACCESSED after the Isochronous TD is retired. This indicates that the Host Controller did not process the Isochronous TD for the frame and therefore did not change the Offset to a PacketStatusWord. When the Host Controller skips the last data packet of Maximum Packet Size from the Isochronous endpoint (64 bytes for a General TD, a more significant error occurs) without having to access system memory. Since the Isochronous TD was not processed in the frame in which it should have been retired, the Isochronous TD remains on its ED’s queue. When the Host Controller processes the Isochronous TD in a latter frame, it finds that the time for expiration of the Isochronous TD has passed. In such casesSimilarly, the Host Controller sets is not allowed to issue an OUT or SETUP token unless it has pre-fetched to an internal buffer all the ConditionCode for data that is sent to the Isochronous TD to DATAOVERRUN and retires the Isochronous TD (it does not, however, set the Halted bit endpoint in the ED). The Host Controller then accesses the next Isochronous TD for the same ED and processes it. Note: Setting DATAOVERRUN in the ConditionCode for the Isochronous TD rather than the PacketStatusWord indicates a time overrun. The same code in a PacketStatusWord will indicate a true data buffer overrun. 0xFFFC 0xFFFE 0xFFFE (-2) 3 Do nothing 0xFFFD 0xFFFE 0xFFFF (-1) 3 Do nothing 0xFFFE 0xFFFE 0x0000 3 Send data packet 0 Host Controller does not process Isochronous TD for three frames due to schedule overrun, then... 0x0002 0xFFFE 0x0004 3 Retire Isochronous TD with DATAOVERRUN in ▇▇▇phase.▇▇

Transfer Errors. Transfer errors for isochronous errors fall into four categories: ?? • transmission ?? • sequence ?? • time ?? • system 4.3.2.3.5.1 Transmission Errors Since there is no handshake for isochronous transfers, the Host Controller can detect transmission errors for transfers only from an endpoint to the host (IN). The error may be either a CRC error, a BITSTUFFING error, or a DEVICENOTRESPONDING error. If any of these errors occurs during the transfer, the ConditionCode of PacketStatusWord[R] is set accordingly and the size field reflects the number of bytes received (up to the size of the buffer defined for the frame) and placed in the memory buffer. For a bit stuffing error, the Host Controller writes up only to the last byte received before the bit stuffing error is detected. If a transmission error is detected along with a sequence or system error, the transmission error is the one that is reported in the ConditionCode ConditionCode. A PID check error in the PID from an endpoint is reported with a ConditionCode of PIDCHECKFAILURE. 4.3.2.3.5.2 Sequence Errors A sequence error occurs when the endpoint sends more or less data than is expected and a transmission error is not present. If the endpoint sends more data than will fit in the specified buffer, the ConditionCode for the PacketStatusWord is set to DATAOVERRUN and the size field is set to the size of the buffer. The Host Controller writes the received data to memory up to the limit of the buffer defined for the frame. If the endpoint sends less data than defined by the buffer, the ConditionCode for the PacketStatusWord is set to DATAUNDERRUN. 4.3.2.3.5.3 Time Errors Each packet has a specific frame in which it is to be transferred. It is possible that the Host Controller cannot start or complete the transfer in the specified frame. There are two manifestations of this type of error: skipped packets and late retirement of an Isochronous TD. Skipped packets occur if the Host Controller does not process an Isochronous TD in a frame for which the Isochronous TD has data. A skipped packet is indicated when an Offset/PacketStatusWord is set to NOT ACCESSED after the Isochronous TD is retired. This indicates that the Host Controller did not process the Isochronous TD for the frame and therefore did not change the Offset to a PacketStatusWord. When the Host Controller skips the last packet of the Isochronous TD, a more significant error occurs. Since the Isochronous TD was not processed in the frame in which it should have been retired, the Isochronous TD remains on its ED’s queue. When the Host Controller processes the Isochronous TD in a latter frame, it finds that the time for expiration of the Isochronous TD has passed. In such cases, the Host Controller sets the ConditionCode for the Isochronous TD to DATAOVERRUN and retires the Isochronous TD (it does not, however, set the Halted bit in the ED). The Host Controller then accesses the next Isochronous TD for the same ED and processes it. Note: Setting DATAOVERRUN in the ConditionCode for the Isochronous TD rather than the PacketStatusWord indicates a time overrun. The same code in a PacketStatusWord will indicate a true data buffer overrun. 0xFFFC 0xFFFE 0xFFFE (-2) 3 Do nothing 0xFFFD 0xFFFE 0xFFFF (-1) 3 Do nothing 0xFFFE 0xFFFE 0x0000 3 Send data packet 0 Host Controller does not process Isochronous TD for three frames due to schedule overrun, then... 0x0002 0xFFFE 0x0004 3 Retire Isochronous TD with DATAOVERRUN in ▇▇▇.▇▇