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 automatically handles 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 comprising:
a bit bucket enable output line connected to said enable terminal; and
a tag logic circuit wherein after an overrun condition exists, said overrun data handling circuit drives a de-asserted signal on said bit bucket enable output line, after detection of a context change by said tag logic circuit, 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.
3. The SCSI host adapter of claim 2 wherein said data overrun data handling circuit further comprises:
a bit bucket disable circuit connected to said status block and having an output terminal.
4. The SCSI host adapter of claim 3 wherein said data overrun data handling circuit further comprises:
a bit bucket control line connected to said output terminal of said bit bucket disable circuit.
5. The SCSI host adapter of claim 4 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.
6. The SCSI host adapter of claim 5 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.
7. The SCSI host adapter of claim 6 wherein said data overrun data handling circuit further comprises:
a context change line connected between said tag logic circuit and said bit bucket enable controller wherein after a signal is asserted on said context change line by said tag logic circuit, 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.
8. The SCSI host adapter of claim 7 wherein said tag logic circuit further comprises:
a bit bucket tag register coupled to said output terminal of said tag logic circuit.
9. The SCSI host adapter of claim 7 wherein said tag logic circuit further comprises:
a current tag register coupled to said output terminal of said tag logic circuit.
10. The SCSI host adapter of claim 8 wherein said tag logic circuit further comprises:
a current tag register coupled to said output terminal of said tag logic circuit.
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;
a plurality of data channels;
a bus phase change status block;
a context done status block;
an overrun data handling circuit comprising:
a bit bucket enable output line connected to said enable terminal;
a bit bucket disable circuit connected to said bus phase change status block and to said context done status block, and having an 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 bit bucket disable circuit 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.
12. The SCSI host adapter of claim 11 further comprising:
a tag logic circuit having an output terminal connected to said context change line.
13. The SCSI host adapter of claim 12 wherein said tag logic circuit further comprises:
a bit bucket tag register coupled to said output terminal of said tag logic circuit.
14. The SCSI host adapter of claim 12 wherein said tag logic circuit further comprises:
a current tag register coupled to said output terminal of said tag logic circuit.
15. The SCSI host adapter of claim 13 wherein said tag logic circuit further comprises:
a current tag register coupled to said output terminal of said tag logic circuit.