V5C Technical Manual
3-4
Bus Grant Daisy Chain
The VMEbus has four bus grant daisy chain signal pairs: BG0IN-/BG0OUT-,
BG1IN-/BG1OUT-, BG2IN-/BG2OUT-, BG3IN-/BG3OUT-. When configuring a
VMEbus P1 backplane, it is necessary to jumper all bus grant daisy chain
signals on the backplane so that the bus grant outputs are connected to the bus
grant inputs at all unused slots. At the slot in which a V5C is installed none of
the bus grant signals should be jumpered. Most VMEbus P1 backplanes provide
an easy method of jumpering the bus grant signals at each card slot position.
Interrupt Acknowledge Daisy Chain
The VMEbus has a single interrupt acknowledge daisy chain signal pair;
IACKIN-/IACKOUT-. As the V5C has an on-board VMEbus interrupter, it
utilizes these signals for determining that a VMEbus acknowledge cycle in
progress is intended for it. Therefore, it is necessary to make sure that the
IACKIN- is not connected to the IACKOUT- at the slot where the V5C is to be
installed. During an interrupt acknowledge cycle, the V5C will intercept the
IACKIN- signal and either respond if it has a pending interrupt at the proper
level, or it will pass the signal on to the next card via the IACKOUT- signal
line. The interrupt controller in non-Slot 1 applications requires the backplane
to have a “wrap-around” path for IACK- to Slot 1. Most VMEbus P1 backplanes
provide an easy method of setting the interrupt acknowledge daisy chain at each
slot.
The Standard P2 Connector
Row
b
of the V5C P2 connector conforms to the VMEbus specification for
A32/D32 operation. SBS Embedded Computers has defined the
a
and
c
rows of
the P2 connector with the signals for SCSI, IDE hard disk, and ST412 floppy
disk interfaces. This is perfectly acceptable and in accordance with VMEbus
specifications. SBS Embedded Computers has a TB-21 Translation Board
which can adapt the row
a
and
c
signals of the P2 to standard SCSI, IDE hard
disk, and ST412 floppy disk connectors. Also, SBS Embedded Computers has
several disk drive modules which can directly connect to the V5C P2 via a
P2-to-P2 cable. This system avoids cables in the card space of a card cage, and
provides flexibility as to the placement of drives and other peripherals. The
pinout of the V5C P2 connector is shown inTable 3-4.
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