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II
MVMEI35A/136A PAL2 SOURCE LISTING
SIGNAL OEseRI PTI ONS
The following outputs may be user customized to fit specific
customer applications.
These PAL equations may be changed if the
customer has requirements for hardware configuration of VMEbus
32/24 address range or 32/16 data space. The target bus (VME or VSB)
may also be hardware configured via this PAL.
It should be noted
that the granularity is limited to ha1f-Mb boundaries. The number
of PAL terms available may also limit the flexibility of the
features prov i ded by th is PAL.
! AOOR23 -
! VSBVME -
!SEGMENT-
B-2
When low, indicates that 24-bit address modifier codes
wi 11
be generated for VMEbus references that fall
within this decoded address.
The equation produces
24-bit address modifier codes when the physical address
is S00000000 through $00FFFFFF and VMEbus cycles occur
(references to thi s address space may be VSBbus as
well).
Bit 2 of control register 5 will affect this
bit.
Refer
to
the
description
of
CNT5
in
the
MVME135/136 hardware manual. This bit is provided as an
aid to configure mixed A24 and A32 slaves in the same
VME chassis.
Used in conjunction with the VSBOEN bit in the VSBCSR.
When VSBOEN is low, the target bus (VME or VSB) will
depend upon this decode output, which when low the bus
access will be explicitly VME or when high explicitly
VSB. The output is currently programmed to alternate on
4Mb boundari es from VSBbus to VMEbus.
Refer to the
descri pt i on
of the VSBOEN
bi t i n
the MVME135/136
hardware
manual
under
the
VSBCSR description
for
further information.
When low, indicates that the decoded address space, for
VMEbus references only, that will be forced to 16 bits.
When
!SEGMENT
is
high,
the
VMEbus
data
width
is
determined by CNT5 bit 1 (refer to the MVME135/136
hardware
for
CNT5
Bit
I).
!SEGMENT
is
~urrent1y
programmed to go low only for VMEbus short I/O bus
cycles and memory mapped I/O bus cycles (see Figure 4-
10). If this bit is not used, it should be programmed to
be a logic
l.
This bit is provided as an aid to
configure 016 and 032 slaves in the same VME chassis.
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