| Title: | VAX on VMEbus: KAV30 |
| Notice: | Could have been as fast as 68K but its a VAX! |
| Moderator: | CSSVMS::KAV30_SUPP |
| Created: | Thu Apr 18 1991 |
| Last Modified: | Fri Aug 02 1996 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 159 |
| Total number of notes: | 645 |
Hello KAV30 users, I have been working on and off with a customer of ours in handling nonexistant memory. His main objective is to determine of one of several digital i/o cards exists on the VMEbus. I have suggested that he use a call to KAV$OUT_MAP and then KAV$BUS_READ to "sniff" if the device is there. The KAV$BUS_READ returns a status which will prevent him from having to use an exception handler just for the check of whether the device is there. He could have used a KAV$BUS_WRITE as the "sniff" since the KAV30 doesn't generate a fatal bugcheck when writing to nonexistant memory as other CVAX based targets do. However, he has run into a strange problem: He can issue a KAV$BUS_READ for a device that doesn't exist and the call will succeed the first time. But a second KAV$BUS_READ to the same address will fail as expected. This situation occurs *only* after he has successfully written to another VMEbus device that does exist. A VMEbus analyzer shows that something is responding to the first KAV$BUS_READ of the nonexistant device. He is going to track further exactly what device is responding. Is there something that he may be inadvertantly doing that causes the KAV30 and its outgoing Scatter Gather Map to erroneously succeed in accessing nonexistant memory on the first try but then correctly fail upon reading the same location in the situation described above? Thanks for any thoughts anyone may have. Alan
| T.R | Title | User | Personal Name | Date | Lines |
|---|---|---|---|---|---|
| 95.1 | BAYERN::WOLFF | Conformism is for little minds. | Mon Jun 28 1993 10:48 | 5 | |
>Is there something that he may be inadvertantly doing that causes the KAV30... Not that I know of. Julian. | |||||
| 95.2 | 'bus-sniffing' works fine for us... | GOBANG::LEMMER | Mon Jul 12 1993 16:17 | 10 | |
Hi Alan, 'bus-sniffing' is used in many applications, we never had any problem.. so we suggest that your customer has an application problem - is it solved already ? Thomas | |||||
| 95.3 | No response from customer yet | ZYDECO::BODA | Realtime Products Support | Mon Jul 12 1993 17:38 | 11 |
Hi Thomas, Unfortunately, I haven't heard back from the customer for several weeks. When I last talked with him, he was going to verify where the signals were coming from using a VMEbus analyzer. Will post a reply here when I get an updated status. Thanks, Alan | |||||