Specifications

Programming the VMEbus Interface
5
5
5-3
Real-Mode “E-page” VMEbus Accesses
The following summarizes the source of the VMEbus address lines for accesses
through the “E” page.
A32
31 24 23
22
21
16
15 0
From
port
8150
From
port
8151
From
port
8130
From
486 address
bits 15-0
A24
23
22
21
16
15 0
From
port
8151
From
port
8130
From
486 address
bits 15-0
A16
15 0
From
486 address
bits 15-0
It should be noted that the EPC-8 drives all 32 address lines even when performing an
A24 or A16 access. Although the VME specification states that boards should not
decode address lines outside their respective address spaces, some boards do anyway.
Because of this, all “unused” high address lines should be set via their respective
registers to all 1’s before a VME data transfer is executed.
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