Appendix B
Programmable Configurations
© National Instruments Corporation
B-3
VME-MXI-2 User Manual
a24_byte_read(202FFE, temp);
} while (temp != (writecount & 0000FF00) >> 8);
a24_byte_write(202FFF, writecount & 000000FF);
do {
a24_byte_read(202FFF, temp);
} while (temp != writecount & 000000FF);
}
else {
/* write limit reached */
print("Write limit reached - can't write.");
}
a24_byte_write(20075B, 01);
/* clear IOCONFIG in VMCR2 */
The following sections describe the features that you can configure by
writing to the EEPROM on the VME-MXI-2.
VME-MXI-2 Requested Memory Space
The VME-MXI-2 requires at least 16 KB of either A24 or A32 space.
You might want to change the amount of space requested or whether
the VME-MXI-2 is an A24 or A32 device. This is especially important
when changing the amount of DRAM installed on the VME-MXI-2.
The amount of space requested by the VME-MXI-2 should match the
amount of DRAM installed. Set it to 16 KB when no DRAM is
installed.
Caution:
If you install DRAM into the VME-MXI-2, do not attempt to use the
first 4 KB of memory space. This 4 KB space maps to the registers on
the VME-MXI-2 and does not access onboard DRAM. Accessing this
region will cause your VME-MXI-2 to behave incorrectly.
If you do not want to lose 4 KB of DRAM you can get around this
limitation by setting the requested memory to double the amount that is
installed on the VME-MXI-2, because the DRAM is aliased throughout
the remainder of the requested memory space. The DRAM should then
be accessed in the upper half of the requested memory space.
To change whether the VME-MXI-2 is an A24 or A32 device, write the
EEPROM byte at offset 2016 hex from the VME-MXI-2 base address.
Write a 4F hex for A24 or a 5F hex for A32.
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