Method and structure for handling packetized SCSI protocol data overruns in a multi-data channel host adapter
View Patent ↗An overrun data handling circuit in a SCSI initiator and an overrun data handling method automatically handle Packetized SCSI Protocol data overruns. A multi-data channel host adapter includes the overrun data handling circuit that automatically handles data overruns for one data context in a Packetized SCSI Protocol data stream without damaging data for other data contexts, in the data stream, for which a data overrun has not occurred.
1. A SCSI host adapter comprising:
a bit bucket circuit including an enable terminal wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after a signal is asserted on said enable terminal; and
an overrun data handling circuit having a bit bucket enable output line connected to said enable terminal wherein after an overrun condition exists, said overrun data handling circuit drives a de-asserted signal on said bit bucket enable output line, after occurrence of a context change, to disable said bit bucket circuit.
2. The SCSI host adapter of claim 1 further comprising:
a plurality of data channels; and
a status block for each data channel in said plurality of data channels.
3. The SCSI host adapter of claim 2 wherein said data overrun data handling circuit further comprises:
a channel bit bucket disable circuit connected to said status block for each data channel in said plurality of data channels, and having a plurality of output lines including an output line for each data channel in said plurality of data channels.
4. The SCSI host adapter of claim 3 wherein said data overrun data handling circuit further comprises:
a channel selector connected to said plurality of output lines of said channel bit bucket disable circuit, and having an output terminal, wherein said channel selector selectively couples and selectively de-couples each output line in said plurality of output lines to said output terminal.
5. The SCSI host adapter of claim 4 wherein said data overrun data handling circuit further comprises:
a bit bucket control line connected to said output terminal of said channel selector.
6. The SCSI host adapter of claim 5 wherein said data overrun data handling circuit further comprises:
a bit bucket enable controller connected to said bit bucket control line and to said bit bucket enable output line.
7. The SCSI host adapter of claim 6 wherein said data overrun data handling circuit further comprises:
a host adapter driver bit bucket enable line connected to said bit bucket enable controller wherein said bit bucket enable controller automatically selectively connects and selectively disconnects said host adapter driver bit bucket enable line to and from said bit bucket enable output line.
8. The SCSI host adapter of claim 6 wherein said data overrun data handling circuit further comprises:
a context change line connected to said bit bucket enable controller wherein after a signal is asserted on said context change line, said bit bucket enable controller drives said de-asserted signal on said bit bucket enable output line of said data overrun data handling circuit independent of a signal level on said host adapter driver bit bucket enable line.
9. A SCSI host adapter comprising:
a bit bucket circuit including an enable terminal wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after a signal is asserted on said enable terminal; and
an overrun data handling circuit having a bit bucket enable output line connected to said enable terminal wherein after an overrun condition exists, said overrun data handling circuit drives a de-asserted signal on said bit bucket enable output line after occurrence of any one of a SCSI bus phase change and a context change.
10. A SCSI host adapter comprising:
a bit bucket circuit including an enable terminal wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after a signal is asserted on said enable terminal; and
an overrun data handling circuit having a bit bucket enable output line connected to said enable terminal wherein after an overrun condition exists, said overrun data handling circuit drives a de-asserted signal on said bit bucket enable output line after occurrence of any one of a SCSI bus phase change, a context change, and a context done.
11. A SCSI host adapter comprising:
a bit bucket circuit including an enable terminal wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after a signal is asserted on said enable terminal; and
an overrun data handling circuit having a bit bucket enable output line connected to said enable terminal wherein after an overrun condition exists, said overrun data handling circuit drives a de-asserted signal on said bit bucket enable output line after occurrence of any one of a SCSI bus phase change and a context done.
12. A SCSI host adapter comprising:
a bit bucket circuit including an enable terminal wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after a signal is asserted on said enable terminal;
a plurality of data channels;
a status block for each data channel in said plurality of data channels;
an overrun data handling circuit comprising:
a bit bucket enable output line connected to said enable terminal;
a channel bit bucket disable circuit connected to said status block for each data channel in said plurality of data channels, and having a plurality of output lines including an output line for each data channel in said plurality of data channels;
a channel selector connected to said plurality of output lines of said channel bit bucket disable circuit, and having an output terminal, wherein said channel selector selectively couples and selectively de-couples each output line in said plurality of output lines to said output terminal;
a bit bucket enable controller connected to said bit bucket enable output line;
a host adapter driver bit bucket enable line connected to said bit bucket enable controller wherein said bit bucket enable controller automatically selectively connects and selectively disconnects said host adapter driver bit bucket enable line to and from said bit bucket enable output line;
a bit bucket control line connected to said output terminal of said channel selector and to said bit bucket enable controller wherein after a signal is asserted on said bit bucket control line, said bit bucket enable controller disconnects said host adapter driver bit bucket enable line from said bit bucket enable output line; and
a context change line connected to said bit bucket enable controller wherein after a signal is asserted on said context change line, said bit bucket enable controller disconnects said host adapter driver bit bucket enable line from said bit bucket enable output line.
13. A method for handling Packetized SCSI Protocol data overruns by a SCSI initiator comprising:
enabling a bit bucket circuit in said SCSI initiator after detecting a data overrun for a data channel in a plurality of data channels of said SCSI initiator wherein said bit bucket circuit automatically generates at least one SCSI acknowledge signal after being enabled; and
disabling, after said detecting said data overrun, said bit bucket circuit after occurrence of a data context change wherein when said disabling occurs before said enabling, said enabling is inhibited.
14. The method of claim 13 wherein said disabling said bit bucket circuit further comprises:
disabling said bit bucket circuit after occurrence of a SCSI bus free state.
15. The method of claim 13 wherein said disabling said bit bucket circuit further comprises:
disabling said bit bucket circuit after occurrence of a SCSI bus phase change.
16. A method for handling Packetized SCSI Protocol data overruns by a SCSI initiator comprising:
enabling a bit bucket circuit in said SCSI initiator after detecting a data overrun for a data channel in a plurality of data channels in said SCSI initiator; and
disabling, after said detecting said data overrun, said bit bucket circuit after occurrence of any one of a data context change, a SCSI bus phase change, and a data context done, wherein when said disabling occurs before said enabling, said enabling is inhibited.
17. A method comprising:
monitoring for a context change in a Packetized SCSI Protocol data stream after a data overrun is detected for one data context in said Packetized SCSI Protocol data stream; and
handling said data overrun for said one data context without damaging another data context in said Packetized SCSI Protocol data stream after detecting a context change.