P R E L I M I N A R Y
AMD
111
Am79C965
Table 37. Slave Accesses
R/W
BE3–BE0
D31–D24
D23–D16
D15–D8
D7–D0
Comments
RD
0000
Data
Double word access to double word
address, e.g. 300, 30C, 310
(DWIO mode only)
RD
1100
Undef
Data
WIO Mode Only: Word access to even
word address, e.g. 300, 30C, 310
RD
0011
Data
Copy
WIO Mode Only: Word access to odd
word address, e.g. 302, 30E, 312
RD
1110
Undef
Data
WIO Mode APROM Read Only: Byte
access to lower byte of even word
address, e.g. 300, 304
RD
1101
Undef
Data
Undef
WIO Mode APROM Read Only: Byte
access to upper byte of even word
address, e.g. 301, 305
RD
1011
Undef
Data
Undef
Copy
WIO Mode APROM Read Only: Byte
access to lower byte of odd word
address, e.g. 302, 306
RD
0111
Data
Undef
Copy
Undef
WIO Mode APROM Read Only: Byte
access to upper byte of odd word
address, e.g. 303, 307
WR
0000
Data
Double word access to double word
address, e.g. 300, 30C, 310
(DWIO mode only)
WR
1100
Undef
Data
WIO Mode Only: Word access to even
word address, e.g. 300, 30C, 310
WR
0011
Data
Undef
WIO Mode Only: Word access to odd
word address, e.g. 302, 30E, 312
Data = indicates the position of the active bytes.
Copy = indicates the positions of copies of the active bytes.
Undef = indicates byte locations that are undefined during the transfer.
EEPROM Microwire Access
The PCnet-32 controller contains a built-in capability for
reading and writing to an external EEPROM. This built-
in capability consists of a microwire interface for direct
connection to a microwire compatible EEPROM, an
automatic EEPROM read feature, and a user-program-
mable register that allows direct access to the microwire
interface pins.
Automatic EEPROM Read Operation
Shortly after the deassertion of the RESET pin, the
PCnet-32 controller will read the contents of the
EEPROM that is attached to the microwire inter-
face. The automatic EEPROM read begins with EECS
being asserted approximately 2.5 EESK periods 2.5
t42
()
following the deassertion of the
RESET pin. Because of
this automatic-read capability of the PCnet-32 control-
ler, an EEPROM can be used to program many of the
features of the PCnet-32 controller at power-up, allow-
ing system-dependent configuration information to be
stored in the hardware, instead of inside of operating
code. PCnet-32 controller interrupt pins will be floated
during H_RESET and will remain floated until either the
EEPROM has been successfully read, or, following an
EEPROM read failure, a Software Relocatable Mode
sequence has been successfully executed.
If an EEPROM exists on the microwire interface, the
PCnet-32 controller will read the EEPROM contents at
the end of the H_RESET operation. The EEPROM con-
tents will be serially shifted into a temporary register and
then sent to various register locations on board the
PCnet-32 controller. System bus interaction will not oc-
cur during the EEPROM read operation after H_RE-
SET, since H_RESET will put the PCnet-32 controller
into a state that will not recognize any I/O accesses and
the PCnet-32 controller will not yet be at an operating
point that requires it to request the bus for bus
mastering.
Thirty-four bytes of the EEPROM are set aside for
PCnet-32 configuration programming and 2 bytes of the
EEPROM are set aside for user programming of logic
that is external to the PCnet-32 controller and may or
may not be pertinent to the operation of the PCnet-32
controller within the system. The user may gain access
to the EEPROM data by snooping the PCnet-32