
312
Registers
Chapter 4
AMD-8111 HyperTransport I/O Hub Data Sheet
24674
Rev. 3.00
April 2003
AMD Preliminary Information
Default:
Bits
31:16
SUBSYSID. Subsystem ID
.
15:0
SUBVENID. Subsystem Vendor ID
.
0000_0000h
Description
Attribute:
Read/write
Note:
This register is aliased to Dev1:0x2C for modifications.
LAN Ethernet Controller Min Grant and Max Latency Alias
Dev1:0xCE
Default:
Bits
15:8
7:0
0000h
Description
MAXLAT. Maximum latency
.
MINGNT. Minimum Grant
.
Attribute:
Read/write
Note:
This register is aliased to Dev1:0x3E for modifications.
4.10.3
Memory-Mapped Registers
The Memory-Mapped Registers give the host CPU access to all programmable features of the device.
These registers are mapped directly into PCI memory space so that any programmable feature can be
accessed with a single PCI memory read or write transaction. Data in these registers can be accessed
as a single byte, a 16-bit word, or a 32-bit double word.
Registers that are logically wider than a double word are shown in the register descriptions as a single
register. These may be accessed using multiple smaller accesses or with a single burst access.
Some registers that are smaller than a double word in width (STVAL, PADR[47:32],
XMT_RING_LEN, RCV_RING_LEN) are placed in the memory map in the lower half of a double
word. The upper half ignores writes and reads back zeros (STVAL, PADR[47:32]) or ones
(XMT_RING_LEN, RCV_RING_LEN) as appropriate for sign extension. This allows these registers
to be accessed with double word reads and writes.
4.10.3.1
Command Style Register Access
The command and interrupt enable registers (CMD0, CMD2, CMD3, CMD7, and INTEN0) use a
write access technique that in this document is called command style access. Command style access
allows the host CPU to write to selected bits of a register without altering bits that are not selected.
Command style registers are divided into 4 bytes that can be written independently. The high order bit
of each byte is the “value” bit that specifies the value that is written to selected bits of the register. The
7 low order bits of each byte make up a bit map that selects which register bits are altered. If a bit in
the bit map is set to 1, the corresponding bit in the register is loaded with the contents of the value bit.
If a bit in the bit map is cleared to 0, the corresponding bit in the register is not altered.