User`s guide

DWMBB/A Module Registers
Page Map Registers (PMRs)
bits<29:0>
Name: Page Frame Number
Mnemonic: PFN
Type: R/W, 0
This field stores a page frame number for address translation for
mapping between the XMI and the VAXBI. When the DWMBB is in
any of the address translation modes, system software must load a
valid PFN entry into this field for the associated PMR of every VAXBI
page it queues for transfer.
How the VAXBI bits concatenate with the appropriate PFN bits to
generate the required XMI address is shown in Table 3–13. Note that
XMI A<39> (the I/O select bit) is always forced to zero.
Table 3–13 Address Translation Bit Mapping (40-bit)
Page Size XMI Address
512 Bytes PFN<29:0> + VAXBI A<8:0> = XMI A<38:0> XMI A<29> = 0
4 Kbytes PFN<26:0> + VAXBI A<11:0> = XMI A<38:0> XMI A<29> = 0
8 Kbytes PFN<25:0> + VAXBI A<12:0> = XMI A<38:0> XMI A<29> = 0
3–97