AM79C978A AMD [Advanced Micro Devices], AM79C978A Datasheet - Page 104

• Manufacturer Part Number: AM79C978A
• Description: Single-Chip 1/10 Mbps PCI Home Networking Controller
• Manufacturer: AMD [Advanced Micro Devices]

1
0
PCI Memory Mapped I/O Base Address Register
Offset 14h
The PCI Memory Mapped I/O Base Address register is
a 32-bit register that determines the location of the
Am79C978A I/O resources in all of memory space. It is
located at offset 14h in the PCI Configuration Space.
Bit
31-5
4
104
MEMSIZE
RES
IOSPACE
Name
MEMBASE Memory mapped I/O base ad-
When the Am79C978A controller
is enabled for memory mapped
I/O mode (MEMEN is set), it mon-
itors the PCI bus for a valid mem-
ory command. If the value on
AD[31:5] during the address
phase of the cycles matches the
value
Am79C978A controller will drive
DEVSEL indicating it will respond
to the access.
MEMBASE is read and written by
the host. MEMBASE is cleared
by H_RESET and is not affected
by S_RESET or by setting the
STOP bit.
MEMSIZE indicates the size of
the
Am79C978A controller requires.
When the host writes a value of
FFFF FFFFh to the Memory
Mapped
Reserved location. Read as zero;
write operations have no effect.
I/O space indicator. Read as one;
write operations have no effect.
Indicating that this base address
register describes an I/O base
address.
Description
dress most significant 27 bits.
These bits are written by the host
to specify the location of the
Am79C978A I/O resources in all
of memory space. MEMBASE
must be written with a valid ad-
dress before the Am79C978A
controller slave memory mapped
I/O mode is turned on by setting
the MEMEN bit (PCI Command
register, bit 1).
Memory mapped I/O size re-
quirements. Read as zeros; write
operations have no effect.
memory
of
I/O
MEMBASE,
Base
space
Address
Am79C978A
the
the
3
2-1
0
PCI Subsystem Vendor ID Register
Offset 2Ch
The PCI Subsystem Vendor ID register is a 16-bit reg-
ister that together with the PCI Subsystem ID uniquely
identifies the add-in card or subsystem the Am79C978A
controller is used in. Subsystem Vendor IDs can be ob-
tained from the PCI SIG. A value of 0 (the default) indi-
cates that the Am79C978A controller does not support
subsystem identification. The PCI Subsystem Vendor
ID is an alias of BCR23, bits 15-0. It is programmable
through the EEPROM.
The PCI Subsystem Vendor ID register is located at
offset 2Ch in the PCI Configuration Space. It is read
only.
PCI Subsystem ID Register
Offset 2Eh
The PCI Subsystem ID register is a 16-bit register that
together with the PCI Subsystem Vendor ID uniquely
identifies the add-in card or subsystem the Am79C978A
controller is used in. The value of the Subsystem ID is
up to the system vendor. A value of 0 (the default) indi-
cates that the Am79C978A controller does not support
subsystem identification. The PCI Subsystem ID is an
alias of BCR24, bits 15-0. It is programmable through
the EEPROM.
MEMSPACE Memory space indicator. Read
PREFETCH Prefetchable. Read as zero; write
TYPE
register, it will read back a value
of 0 in bit 4. That indicates a
Am79C978A memory space re-
quirement of 32 bytes.
operations have no effect. Indi-
cates that memory space con-
trolled by this base address
register is not prefetchable. Data
in the memory mapped I/O space
cannot be prefetched. Because
one of the I/O resources in this
address space is a Reset regis-
ter, the order
accesses is important.
zeros; write operations have no
effect. Indicates that this base ad-
dress register is 32 bits wide and
mapping can be done anywhere
in the 32-bit memory space.
as zero; write operations have no
effect. Indicates that this base ad-
dress register describes a memo-
ry base address.
Memory type indicator. Read as
of the read