8/01/00
Am79C976
195
P R E L I M I N A R Y
by S_RESET or setting the STOP
bit.
3
RWU_DRIVER RWU Driver Type. If this bit is set
to 1, RWU is a totem pole driver;
otherwise RWU is an open drain
output.
Read/Write accessible. Cleared
by H_RESET and is not affected
by S_RESET or setting the STOP
bit.
2
RWU_GATE RWU Gate Control. If this bit is
set, RWU is forced to the high Im-
pedance State when PG is LOW,
regardless of the state of the
MPMAT and LCDET bits.
Read/Write accessible. Cleared
by H_RESET and is not affected
by S_RESET or setting the STOP
bit.
1
RWU_POL RWU Pin Polarity. If RWU_POL
is set to 1, the RWU pin is normal-
ly HIGH and asserts LOW; other-
wise, RWU is normally LOW and
asserts HIGH.
Read/Write accessible. Cleared
by H_RESET and is not affected
by S_RESET or setting the STOP
bit.
0
RST_POL
PHY_RST Pin Polarity. If the
PHY_POL is set to 1, the
PHY_RST pin is active LOW; oth-
erwise,
PHY_RST
HIGH.
is active
Read/Write accessible. Cleared
by H_RESET and is not affected
by S_RESET or setting the STOP
bit.
/-
Bit
Name
Description
31-0
RES
Reserved locations. Written as
zeros and read as undefined.
(
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-2
RES
Reserved locations. Written as
zeros and read as undefined.
0
RCVALGN
Receive Packet Align. When set,
this bit forces the data field of ISO
8802-3 (IEEE/ANSI 802.3) pack-
ets to align to 0 MOD 4 address
boundaries (i.e., DWord aligned
addresses). It is important to note
that this feature will only function
correctly if all receive buffer
boundaries are DWord aligned
and all receive buffers have 0
MOD 4 lengths. In order to ac-
complish the data alignment, the
Am79C976 controller simply in-
serts two bytes of random data at
the beginning of the receive
packet (i.e., before the ISO 8802-
3 (IEEE/ANSI 802.3) destination
address field). The MCNT field
reported to the receive descriptor
will not include the extra two
bytes.
Read/Write
RCVALGN
H_RESET or S_RESET and is
not affected by STOP.
accessible.
cleared
is
by
Bit
Name
Description
31-0
RES
Reserved locations. Written as
zeros and read as undefined.
"
This register is used to place the Am79C976 controller
into various test modes. The Runt Packet Accept is the
only user accessible test mode. All other test modes are
for AMD internal use only.
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-4
RES
Reserved locations. Written as
zeros and read as undefined.
3
RPA
Runt Packet Accept. This bit forc-
es the Am79C976 controller to
accept runt packets (packets
shorter than 64 bytes).
The minimum packet size that
can be received is 12 bytes.