
8/01/00
Am79C976
207
P R E L I M I N A R Y
affected by S_RESET or setting
the STOP bit.
3
RES
Reserved location. Written and
read as zeros.
2
RCVE
Receive Status Enable. When
this bit is set, a value of 1 is
passed to the LEDOUT bit in this
register when there is receive ac-
tivity on the network.
Read/Write accessible. RCVE is
cleared by H_RESET and is not
affected by S_RESET or setting
the STOP bit.
1
SFBDE
Start Frame/Byte Delimiter En-
able. When this bit is set, a value
of 1 is passed to the LEDOUT bit
in this register when the RXD[3:0]
pins are presenting the least sig-
nificant nibble of valid frame data.
Read/Write accessible. RCVE is
cleared by H_RESET and is not
affected by S_RESET or setting
the STOP bit.
0
COLE
Collision Status Enable. When
this bit is set, a value of 1 is
passed to the LEDOUT bit in this
register when there is collision
activity on the network.
Read/Write accessible. COLE is
set to 1 by H_RESET and is not
affected by S_RESET or setting
the STOP bit.
2-*'&
Note:
Bits 15-0 in this register are programmable
through the EEPROM.
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-3
RES
Reserved locations. Written as
zeros and read as undefined.
2
FDRPAD
Full-Duplex Runt Packet Accept
Disable. When FDRPAD is set to
1 and full-duplex mode is en-
abled, the Am79C976 controller
will only receive frames that meet
the minimum Ethernet frame
length of 64 bytes. Receive DMA
will not start until at least 64 bytes
or a complete frame have been
received. When FDRPAD is
cleared to 0, the Am79C976 con-
troller will accept any frame of 12
bytes or greater, and receive
DMA will start according to the
programming of the receive FIFO
watermark.
Read/Write accessible. FDRPAD
is set to 1 by H_RESET and is not
affected by S_RESET or by set-
ting the STOP bit.
1
RES
Reserved locations. Written as
zeros and read as undefined.
0
FDEN
Full-Duplex Enable. FDEN con-
trols whether full-duplex opera-
tion is enabled. When FDEN is
cleared and the Auto-Negotiation
is disabled, full-duplex operation
is
not
enabled
Am79C976 controller will always
operate in the half-duplex mode.
When
FDEN
Am79C976 controller will operate
in full-duplex mode when the MII
port is enabled.
Do not set this
bit when Auto-Negotiation is
enabled
.
and
the
is
set,
the
Read/Write accessible. FDEN is
reset to 0 by H_RESET, and is
unaffected by S_RESET and the
STOP bit.
, <8
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-5
IOBASEL
Reserved
H_RESET, the value of these bits
will be undefined. The settings of
these bits will have no effect on
any Am79C976 controller func-
tion. It is only included for soft-
ware compatibility with other
PCnet family devices.
locations.
After
Read/Write
BASEL
S_RESET or STOP.
accessible.
not
affected
IO-
by
is
4-0
RES
Reserved locations. Written as
zeros, read as undefined.