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VME FAQ Questions
Q12. What is the difference between VME64 and VME64x?
Q13. How can I tell if my Themis VME card is VME64 or VME64x?
Q14. Should I plug my Themis VME card into a 3-row or 5-row
backplane?
Q15. Some VME signals are "bussed", some are "daisy-chained",
and some are neither. Should I care?
Q16. What does it mean if a VME chassis is "auto-jumpering"?
Or not "auto-jumpering"? How can I tell which one my chassis
is?
Q17. Is "SYSCON" the same thing as "Master" or "Bus Master"?
Q18. More than one card is reporting to be the SYSCON, what's
wrong?
Q19. No cards are booting up as SYSCON, what's wrong?
Q20. Can I have SYSCON in the middle of several VME cards,
or over on the far right?
Q21. Sanity check: Can I conveniently test a few VME read
or write cycles with OBP commands?
Q22. Sanity check: Can I conveniently test a few VME read
or write cycles with Solaris commands?
VME Questions and Answers (for Appendix information
see link at bottom of page)
Q12. What is the difference between
VME64 and VME64x?
A12. VME64 Extensions (VME64x) is a set of extra features
added to the VME64 specification. Nearly all of the new features
are optional, only two must be implemented to claim VME64x
compatibility. Refer to Appendix B, section B2.1 and B2.2.
Q13. How can I tell if my Themis
VME card is VME64 or VME64x?
A13. Check the hardware manual to find out for sure.
But all Themis VME cards since 1998 are at least VME64. The
newer models are VME64x, indicated by the extra conductor
"fingers" located on the outside of the VME connector
shells. Refer to Appendix B, section B2.1 and B2.2.
Q14. Should I plug my Themis VME
card into a 3-row or 5-row backplane?
A14. Either one will work, they are both forward and
backward compatible. However, putting a 5-row card in a 3-row
chassis will result in losing special features (if any) provided
by the two extra rows. Refer to Appendix B, section B2.1 and
B2.2.
Q15. Some VME signals are "bussed",
some are "daisy-chained", and some are neither. Should I care?
A15. A bussed VME signal makes connection to every
slot in the VME backplane. A daisy-chained signal only connects
two adjacent slots. Some signals don't connect to anything
(e.g. - user-defined pins on P2/J2 connector). Generally these
signals don't need any special attention, except perhaps for
the daisy-chained signals in a non-auto-jumpering chassis.
Refer to Appendix B, section B2.3.
Q16. What does it mean if a VME
chassis is "auto-jumpering"? Or not "auto-jumpering"? How
can I tell which one my chassis is?
A16. An auto-jumpering VME backplane will automatically
take care of propagating the 5 daisy-chained VME signals across
a vacant VME slot. (This is also called automatic daisy-chaining.)
If the backplane is not auto-jumpering then the user must
manually propagate the 5 daisy-chained signals across vacant
VME slots. Refer to Appendix B, section B2.3.
An auto-jumpering backplane usually has an IC chip or two
adjacent to each J1 connector that implements the auto-jumpering
capability, but not always. The IC chip(s) can be on the front
or the back of the backplane. Refer to Appendix B, section
B2.3 for additional details.
Q17. Is "SYSCON" the same thing as "Master" or "Bus Master"?
A17. No, system controller (SYSCON) is an entirely
separate concept from bus master. On any given VME backplane
there must be exactly one SYSCON, normally occupying the left-most
slot. The SYSCON assumes system controller duties at the power-up
event and must maintain these duties until power-off. In contrast,
any VME board installed on the backplane can become a bus
master (assuming it has bus master capability), it can "own"
the bus for a period of time to perform read and/or write
cycles. Then it relinquishes bus ownership so that a different
board can have its turn as bus master. At any given instant
that can be either zero or one bus master.
Q18. More than one card is reporting
to be the SYSCON, what's wrong?
A18. All Themis VME cards can be configured to automatically
detect if they should be the SYSCON. This "auto-SYSCON"
function is common in many other VME cards as well. But some
boards must be manually configured to enable or disable their
SYSCON capability. If more than one card is reporting that
it has assumed SYSCON duty then perhaps one of them is an
incorrectly configured "manual" SYSCON board. Also,
you may encounter multiple SYSCON boards if the BG3IN*/BG3OUT*
daisy-chained signal is not propagated down the backplane
(automatic SYSCON capability is implemented using the BG3IN*
signal). Refer to Appendix B, section B2.4 for additional
information.
Q19. No cards are booting up as
SYSCON, what's wrong?
A19. Themis VME cards have an optional jumper that
inhibits SYSCON function. Make sure this jumper is not installed.
Other VME cards often have a jumper that does the same thing,
verify their configuration. One other possibility is that
something is wrong with the BG3IN*/BG3OUT* daisy-chained signal.
An "auto-SYSCON" VME card samples BG3IN* shortly
after power-up to determine whether or not it should be the
SYSCON. If BG3IN* is low then it becomes SYSCON and drives
BG3OUT* high to prevent any other card from becoming SYSCON.
If the BG3IN* pull-down resistor is damaged there could be
a problem, or if the left-most slot is unoccupied and BG3IN*
is not jumpered to BG3OUT* then that could also cause a problem.
Q20. Can I have SYSCON in the middle
of several VME cards, or over on the far right?
A20. No, SYSCON must be the left-most card in the chassis,
normally occupying slot #1. Refer to Appendix B, section B2.4
for additional details.
Q21. Sanity check: Can I conveniently
test a few VME read or write cycles with OBP commands?
A21. Yes, consult your Themis VME hardware manual for
an example. (Other examples are in work and will be placed
in Appendix B at a future date).
Q22. Sanity check: Can I conveniently
test a few VME read or write cycles with Solaris commands?
A22. Yes. Refer to example program vme_rw included
with the Themis VME nexus driver. (Other examples are in work
and will be placed in Appendix B at a future date).
To download Themis
Board and System FAQ Questions, Answers and Appendix A-B information,
please click here.
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