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Adapter Internal Registers
A-23
Register Definitions
A.3.1 Network Command Register–NetCmd @ 0x00 (DIO)
All bits in this register are set to 0 on an Ad_Rst or when PRST# is asserted.
01234567
TXPACETRFRAMDUPLEXNOBRXCAFCSFNWRAPNRESET
Byte 0
Table A–8. Network Command Register Bits
Bit Name Function
7 NRESET ThunderLAN controller not reset: This bit is set to a 1 or a 0 by DIO. This bit is set to a
0 (active) by an Ad_Rst or a PCI reset. When this bit is set to a 0, the ThunderLAN con-
troller is kept in a reset state. Network configuration in the NetConfig register can only
be altered while this bit is set to a 0.
6 NWRAP Not wrap: This bit determines the flow of data to and from the adapter. This bit is set to
a 0 (active) by an Ad_Rst or by a PCI reset. If this bit is set to a 0, data is internally
wrapped by the adapter and does not pass through the MII or internal PHY. If this bit is
set to 1, network Rx and Tx data pass the selected network PHY.
In internal wrap mode, the adapter media access control (MAC) logic is clocked by the
PCI bus clock. All network clocks are ignored, and all MII pins, except MDCLK/MDIO,
are placed in the high-impedance state.
†
5 CSF Copy short frames/copy routed frames: The function of this bit depends on the MAC pro-
tocol in use:
CSMA/CD mode: If this bit is set, the receiver does not discard frames that are
shorter than a slottime (64 bytes).
Demand priority/token ring mode: This bit has no function.
4 CAF Copy all frames: When this bit is set to 1, the ThunderLAN controller receives frames
indiscriminantly, without regard to destination address. CAF does not copy error frames
unless the PEF bit in the NetConfig register is set.
3 NOBRX No broadcast Rx: When this bit is set to 1, the ThunderLAN controller does not receive
frames with broadcast addresses (such as 0xffff.ffff.ffff, the all nodes broadcast address;
or 0xC000.ffff.ffff, the token ring all nodes for this ring broadcast address). When this bit
is set to 0, broadcast frames are received by the adapter.
2 DUPLEX Full duplex: When this bit is set to 1
‡
, the ThunderLAN controller transmits and receives
frames simultaneously in full duplex. When this bit is set to 0, the ThunderLAN controller
transmits and receives frames in half duplex.
1 TRFRAM Token ring frame format: When this bit is set to 1, the ThunderLAN controller uses the
token ring frame format for all frames transmitted or received. When this bit is set to 0,
the ThunderLAN controller uses the Ethernet frame format for all frames transmitted or
received.
†
Because this bit directly switches the network logic clocks, it should only be changed while NRESET is active.
‡
Collision statistics are disabled in full duplex.