4. Register Descriptions
117
Tsi308 User Manual
80D4000_MA001_02
Tundra Semiconductor Corporation
www.tundra.com
6
R/W
0
SecBusReset:
If written to a 1, hardware will perform a reset sequence on the secondary bus.
Clearing the bit will bring the secondary bus out of reset. Not persistent through
warm reset.
5
R/W
0
MstrAbortMode:
This bit controls the action taken by the bridge when a transaction that it is
forwarding in either direction takes a master abort on the destination bus. The
master abort is indicated on HyperTransport by an error response with NXA set
If this bit is clear, writes are allowed to complete normally on the source bus, and
reads have all 1’s returned.
SP/DSP:
If it is set, the master abort will be treated as an error, returning error, returning a
Target Abort Response (indicated on HyperTransport by a set error bit without NXA)
for nonposted requests and causing a sideband error assertion (indicated by
asserting the FATAL_ERR_N or NONFATAL_ERR_N interrupt pins, as enabled) for
posted requests.
GSP/ GDP:
If it is set, the master abort will be treated as an error, returning error, returning a
Target Abort Response (indicated on HyperTransport by a set error bit without NXA)
for nonposted requests.
For posted requests Tsi308 floods both the HT links with sync packets if SERR#
Enable bit in the Command register is set.
Not persistent through warm reset.
4
R
0
Reserved.
3
R/W
0
VgaEn:
This bit modifies the response by the bridge to VGA compatible addresses, which
are defined as memory addresses in the range 0_000A_0000h – 0_000B_FFFFh,
and I/O space addresses in the bottom 64KB of PCI I/O space, where the bottom 10
bits are in the range 3B0h – 3BBh or 3C0h - 3DFh. Address bits 15:10 of I/O
addresses are not decoded, allowing for ISA aliasing of the above address ranges.
If set, the bridge will forward these addresses from the primary to the secondary bus
and block forwarding them from the secondary to the primary bus; regardless of the
contents of the memory and I/O range registers, the ISA Enable bit (in this register),
or the VGA Palette Snoop Enable bit (in the Command register).
Not persistent through warm reset.
If this bit is set when the address mapping extensions are in use, the address
decode behavior or the device may be undefined
Bit
R/W
Access
Initial
Value
Field Name and Description
Summary of Contents for TSI308
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