User`s guide

DWMBB Adapter

3.9 Programmable VAXBI I/O Window Space

The DWMBB can be programmed so that the location of VAXBI

I/O window space is independent of the XMI node. This feature

is enabled by setting a bit in the Control and Status Register and

loading an address in the Utility Register used to calculate the

base address of the I/O window space.

VAXBI I/O window space is the window for XMI commanders to nodes on

the VAXBI. This is a 32-Mbyte range located in the lower 512 Mbytes of

XMI I/O address space. The base address of this window space normally

depends on the XMI node ID and the VAXBI node ID. At power-up and

node reset, the DWMBB defaults to the following equation to determine if

an I/O request is within its VAXBI I/O window space:

For 32-bit address:

bb = E000 0000 + (200 0000 * XMI Node ID) + (2000 * VAXBI Node ID)

For 30-bit address:

bb = 2000 0000 + (200 0000 * XMI Node ID) + (2000 * VAXBI Node ID)

The DWMBB can select the location of the VAXBI I/O window space in

XMI I/O address space so that it is independent of the XMI node ID.

The software programmable ﬁeld VAXBI Window Space (AUTLR<13:0>)

enables the VAXBI I/O window space to be moved to any 32-Mbyte aligned

boundary in the 512-Mbyte range of extended XMI I/O address space.

When the VAXBI Window Space Enable bit (ACSR<5>) is set, the DWMBB

uses the value loaded in the VAXBI Window Space ﬁeld to calculate

the new location for the VAXBI I/O window space, using the following

equation:

For 32-bit address:

bb = E000 0000 + (200 0000 * AUTLR<13:0>) + (2000 * VAXBI Node ID)

For 30-bit address:

bb = 2000 0000 + (200 0000 * AUTLR<13:0>) + (2000 * VAXBI Node ID)

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