Download Digital Equipment Corporation AlphaPC64 User guide

The scatter-gather RAM is an 32K n longword page in memory space. The top
27 bits are read/write; the remaining 5 bits are MBZ. Scatter-gather RAM is
not initialized by hardware and starts up in a random state. Firmware must
initialize this area to a default state before using the VME subsystem.
The scatter-gather RAM is fully programmable over the PCI bus. The mapping of
the scatter-gather RAM takes up 128 KB of PCI memory space and has its own
base address.
The 8K scatter-gather longword entries are in three regions:
Entry
Address
Each Entry Maps:
Index Formed By:
2048 A24
inbound
VME_SG_BASE +
10000h
8K page of A24 VME
address space into PCI
address space
VME A24 <23:13>
16384 A32
inbound
VME_SG_BASE
8K page of A32 VME
address space into PCI
address space
VME A32 <26:13>
2048
outbound
VME_SG_BASE +
1E000h
256K page of PCI
memory into VMEbus
Depends on region
used for master
access:
VME_WINDOW :
PCI <28:18>
VME_SUB_
WINDOW (64 MB) :
PCI <25:18>
10.5.3 Configuring the VIC64
The address map for the VIC64 places the VIC registers in byte 3 of a particular
longword address. As used by a Digital Alpha VME 4 system, the VIC registers
are seen at byte zero in each longword, when accessed over the PCI bus.
VIICR
Bits 2-0
Local interrupt priority level (IPL) setting for VMEbus interrupter
acknowledge received interrupt.
Bits 6-3
Reserved, must read as 1s.
Bit 7
Interrupt mask bit.
VICR1-7
Bits 2-0
Local IPL setting for VMEbus interrupt.
Bits 6-3
Reserved, must read as 1s.
Bit 7
Interrupt mask bit.
10–32 VME Interface