Publication No. SBC330-0HH/3
FPGA Registers 55
6.6 Geographic Address Register
The
VPX
specification
defines
a
total
of
six
backplane
pins
for
Geographical
addressing.
There
are
six
Geographic
Addressing
signals
in
the
VPX
specification.
The
SBC330
pulls
all
the
Geographic
address
lines
high;
the
backplane
either
ties
them
low
or
lets
them
float
according
to
the
slot
number,
so
each
slot
has
a
specific
address.
The
GAP
signal
is
a
parity
signal,
which
dictates
that
the
number
of
pins
tied
to
ground
is
odd.
Software
can
check
that
the
global
address
is
valid.
‘0’
is
the
‘active’
level.
Hence
from
the
VPX
specification:
Table 6-2
Slot
GA[01234] GAP
Slot 1
01111 1
Slot 2
10111 1
Slot 3
00111 0
Chip
Select
CS2
Offset
0x001C
LAD Bit
Reg Bit
R/W
Description
Reset Value
15
0
R
GLOB_A(0)
Slot dependent
14
1
R
GLOB_A(1)
Slot dependent
13
2
R
GLOB_A(2)
Slot dependent
12
3
R
GLOB_A(3)
Slot dependent
11
4
R
GLOB_A(4)
Slot dependent
10
5
R
GLOB_AP
Slot dependent