GE PCIE-5565PIORC* Hardware Reference Manual page 65

65 PCIE-5565PIORC Reflective Memory Board
space. This gives the user application PIO access to the Reflective Memory
locations $00000000 up to $001FFFFF. The user application can set the Local Base
Address (Remap) register pointing to any valid window in the installed memory.
For example, the user application can write $00200000 to the Remap register to
access the second 2 MByte PCI PIO window. The register value will be $00200001
since bit‐0 is hardwired to 1. This gives the user application PIO access to the
Reflective Memory locations $00200000 up to $003FFFFF. The user application
uses the same PCIBAR3 window ranging from $F7600000 up to $F77FFFFF.
NOTE
After writing a new value to the LAS1BA remap register, the user application should read the
LAS1BA remap register before accessing the new window. This ensures the new window mapping
has taken effect and subsequent memory accesses will be to the new memory window.
In summary, register LAS1RR is the range register corresponding to the size of the
PCI window and is read‐only. Register LAS1BA is the writeable base address
register. It is used to remap or offset the PCI PIO window to access other sections
of the installed memory. The RFM‐5565 firmware prevents the user from entering
an invalid Remap Value. The value written must be a multiple of the PCI window
size. For example, using a PCI window size of 2 MByte with 64 MByte of installed
memory means there are 32 valid base address settings from $00000000 to
$03E00000, incrementing by $00200000 (all other bits are masked off when
written). Also, a 64 MByte card with a 64 MByte window has no valid base
address settings other than the default 0.
Since the PCI window size and the Remap register only affect PCI PIO accesses,
DMA (Local‐to‐PCI and PCI‐to‐Local) can be used normally to transfer up to
$7FFFFF bytes with another location on the PCI bus regardless of the Remap
value.