Peritek
5-8
Programming On-board Devices and Memories
5.2.3 A32 Address Map and the XARADR Address Match Register
The graphics board has an extended addressing function which allows a
VMEbus host to linearly access the board through a 64 MB block in A32
space. You can access all on-board devices and memory through this
block. Except for PX Windows multiprocessor drivers, Peritek software
does not use A32 access.
In order for the A32 space on the board to respond the XARADR register
must be set up with a valid address, the 34020 must be initialized, and
CSR bit
XMEMON
must be set.
Caution
Do not set XMEMON until
after
the XARADR has been set up.
The hardware byte-swapping function can be enabled for A32 space. You
must first set the
A32SWAPEN
bit in the CSR.
Note that the A32 space
usage increases to 256 MB when A32 byte swapping is enabled.
The
reason for this is revealed in Section 5.3.5, which contains detailed
information on the byte swapping.
The XARADR/DBRADR Address Match Registers are programmed
through a single register in the CSR block. Which register is accessed
through the register slot is controlled by the
XARSEL
bit in the CSR..
When XARSEL = 1, the XARADR address match register is selected.
Table 5-4 XARADR Address Match Register
A32 Space
XARADR
Address Bit
Data Bit
R/W
Reset
26
0
yes
SYSRESET
27
1
yes
SYSRESET
28
2
yes
SYSRESET
29
3
yes
SYSRESET
30
4
yes
SYSRESET
31
5
yes
SYSRESET
--
6-31
reads 0
no
Note
When A32SWAPEN is set, XARADR 0 and 1 are don't care.
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