am79c970 Advanced Micro Devices, am79c970 Datasheet - Page 109

• Manufacturer Part Number: am79c970
• Description: Pcnettm-pci Single-chip Ethernet Controller For Pci Local Bus
• Manufacturer: Advanced Micro Devices

Bus Configuration Registers
The Bus Configuration Registers (BCR) are used to pro-
gram the configuration of the bus interface and other
special features of the PCnet-PCI controller that are not
related to the IEEE 8802-3 MAC functions. The BCRs
are accessed by first setting the appropriate RAP value,
and then by performing a slave access to the BDP.
All BCR registers are 16 bits in width in WIO mode and
32 bits in width in DWIO mode. The upper 16 bits of all
BCR registers is undefined when in DWIO mode. These
bits should be written as ZEROs and should be treated
as undefined when read. The Default value given for any
BCR is the value in the register after H_RESET, and is
hexadecimal unless otherwise stated. BCR register val-
ues are unaffected by S_RESET and are unaffected by
the assertion of the STOP bit.
1-976
* Registers marked with an “*” have no default value, since they are not observable without first being programmed through the
EEPROM read operation or a user register write operation. Therefore, the only observable values for these registers are those
that have been programmed and a default value is not applicable.
8–15
BCR
AMD
16
17
18
19
20
21
0
1
2
3
4
5
6
7
MNEMONIC
IOBASEU
Reserved
Reserved
IOBASEL
MSWRA
INTCON
MSRDA
EECAS
LNKST
BSBC
LED1
LED2
LED3
SWS
MC
Default
00C0h
0005h
0005h
0084h
0088h
0090h
2101h
0002h
0000h
N/A*
N/A*
N/A*
N/A*
N/A
N/A
P R E L I M I N A R Y
Description
Reserved
Reserved
Miscellaneous Configuration
Reserved
Link Status Status (Default)
Receive Status (Default)
Reserved
Transmit Status (Default)
Reserved
Reserved
Reserved
Burst Size and Bus Control
EEPROM Control and Status
Software Style
Reserved
Am79C970
Note that several registers have no default value. BCR3
and BCR8-15 are reserved and have undefined values.
BCR2, BCR16, BCR17 and BCR21 are not observable
without first being programmed through the EEPROM
read operation or a user register write operation. There-
fore the only observable values for these registers are
those that have been programmed and a default value is
not applicable.
BCR0, BCR1, BCR6, BCR16, BCR17, and BCR21 are
reserved in the PCnet-PCI controller. These registers
are used by other devices in the PCnet family. Writing to
these registers have no effect on the operation of the
PCnet-PCI controller.
Writes to those registers marked as “Reserved” will
have no effect. Reads from these locations will produce
undefined values.
User
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
No
No
No
No
EEPROM
Yes
Yes
Yes
Yes
Yes
No
No
No
No
No
No
No
No
No
No