AM79C965A Datasheet, PDF (104/228 Pages) –

Software Access
I/O Resources
PCnet-32 Controller I/O Resource Mapping
The PCnet-32 controller has several I/O resources.
These resources use 32 bytes of I/O space that begin
at the PCnet-32 controller I/O Base Address. The
PCnet-32 controller allows two modes of slave access.
Word I/O mode treats all PCnet-32 controller I/O
Resources as two-byte entities spaced at two-byte ad-
dress intervals. Double Word I/O mode treats all
PCnet-32 controller I/O Resources as four-byte entities
spaced at four-byte address intervals. The selection of
WIO or DWIO mode is accomplished by one of two
ways:
1. H_RESET function.
2. The PCnet-32 controller I/O mode setting will
default to WIO after H_RESET (i.e. DWIO = 0).
3. Automatic determination of DWIO mode due to
double-word I/O write access to offset 10h.
DWIO is automatically programmed as active when the
system attempts a double word write access to offset
10h of the PCnet-32 controller I/O space. Note that this
space corresponds to RDP, regardless of whether
DWIO or WIO mode has been programmed. The power
up H_RESET value of DWIO will be ZERO, and this
value will be maintained until a double word access is
performed to PCnet-32 controller I/O space.
Therefore, if DWIO mode is desired, it is imperative that
the first access to the PCnet-32 controller be a double
word write access to offset 10h.
Alternatively, if DWIO mode is not desired, then it is im-
perative that the software never executes a double
word write access to offset 10h of the PCnet-32
controller I/O space.
Once the DWIO bit has been set to a ONE, only a
H_RESET can reset it to a ZERO.
The DWIO mode setting is unaffected by S_RESET or
the STOP bit.
WIO I/O Resource Map
When the PCnet-32 controller I/O space is mapped as
Word I/O, then the resources that are allotted to the
PCnet-32 controller occur on word boundaries that are
offset from the PCnet-32 controller I/O Base Address
as shown in Table 32.
Table 32. Word I/O Mapping
Offset
(Hex)
0
2
4
8
A
C
E
10
12
14
16
18
1A
1C
1E
No. of
Bytes
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
Register
Address PROM
Address PROM
Address PROM
Address PROM
Address PROM
Address PROM
Address PROM
RDP
RAP (shared by RDP and BDP)
Reset Register
BDP
Vendor Specific Word
Reserved
Reserved
Reserved
When PCnet-32 controller I/O space is Word mapped,
all I/O resources fall on word boundaries and all I/O re-
sources are word quantities. However, while in Word I/
O mode, address PROM accesses may also be
accessed as individual bytes on byte addresses.
Attempts to write to any PCnet-32 controller I/O re-
sources (except to offset 10h, RDP) as 32 bit quantities
while in Word I/O mode are illegal and may cause
unexpected reprogramming of the PCnet-32 controller
control registers. Attempts to read from any PCnet-32
controller I/O resources as 32-bit quantities while in
Word I/O mode are illegal and will yield undefined
values.
An attempt to write to offset 10H (RDP) as a 32 bit
quantity while in Word I/O mode will cause the
PCnet-32 controller to exit WIO mode and immediately
thereafter, to enter DWIO mode.
Accesses to non-word address boundaries are not
allowed while in WIO mode, with the exception of the
APROM locations. The PCnet-32 controller may or may
not produce an LDEV and a RDY signal in response to
such accesses, but data will be undefined.
Accesses of non-word quantities to any I/O resource
are not allowed while in WIO mode, with the exception
of byte reads from the APROM locations. PCnet-32
controller may or may not produce an LDEV and will not
produce a RDY signal in response to such accesses,
but data will be undefined.
The Vendor Specific Word (VSW) is not implemented
by the PCnet-32 controller. This particular I/O address
is reserved for customer use and will not be used by
future AMD Ethernet controller products. If more than
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Am79C965A