Data General AViiON 5000 Series, Клиентская документация

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Assigning VME Data Bus and Interrupt Priorities
E-7
014–001867
2. Do not have empty slots between the arbiter and the last board on the VMEbus.
This rule precludes an empty slot before the first VME board as well as empty
slots between boards in the system.
NOTE: If, for any reason, you must have empty slots between VMEbus
controllers, those slots must have their Bus Grant and Interrupt
Request lines jumpered over on the back panel.
3. Group together all VMEbus controllers that have the same fixed priority levels.
Organize the groups by descending order of DTB priority: level 0 priority group
first (closest to the arbiter), level 1 priority group next, and so on. This approach
reduces the daisy chain priority signal etch length between loads.
4. The recommended board position within a VME DTB Group is defined by the
order of the board in Table E–1 from top to bottom, with the top being closest to
the arbiter. Remember position priority is only at an individual fixed priority
level (Figure E–1). A level 3 board always has priority over a level 2, 1, or 0
board, no matter what their position within the system is relative to each other.
NOTE: Table E–1 lists the relative priorities of VMEbus controllers to aid you in
your priority assignments. In this table, the priority relationship between
boards is indicated numerically by numbers that range from 1 to 9, with 1
being the highest priority. If two or more descriptions have the same
number, then their priority with respect to each other is irrelevant. If you
are not sure about how to use Table E–1, contact your Data General
technical support office.
Table E–1 Relative Priorities of VMEbus Controllers
Recommended
Relative
General Description Priority
VME boards that are VMEbus SLAVE only devices (VLC) N/A*
Board will lose data if VMEbus is not available. 1
System function is affected if board is denied access to the VMEbus 2
Synchronous communication controller (VSC or VSC/3) 3
Asynchronous communications controller (VAC/16 or VTC) 4
IEEE 802.3 controller (Ethernet) (VLCi) 5
IEEE 802.5 controller (Token Ring) (VTRC) 5
Communications controller (VDA/128 or VDA/255)) 5
SCSI 1 interface w/slow devices attached (< 500KB/s) 6
SCSI 2 interface w/slow devices attached (< 500KB/s) (VSA) 6
SCSI 1 interface w/fast devices attached (> 500KB/s) 7
SCSI 2 interface w/fast devices attached (> 500KB/s) (VSA) 8
FDDI communication controller (VFC) 9
* Same as arbiter
Recommended DTB Priorities
Table E–2 lists the recommended (also the default) Bus Grant priority settings for
VME controllers in Data General Systems.