DP83932C datasheet(28/98 Pages) NSC

28 / 98 page

40 SONIC Registers (Continued)

43 REGISTER DESCRIPTION

(Continued)

431 Command Register

(Continued)

Bit

Description

RXEN RECEIVER ENABLE

Setting this bit enables the receive buffer management engine to begin buffering data to memory Setting this bit

resets the RXDIS bit Note If this bit is set while the MAC unit is currently receiving a packet both RXEN and RXDIS

are set until the network goes inactive (ie the SONIC will not start buffering in the middle of a packet being

received)

RXDIS RECEIVER DISABLE

Setting this bit disables the receiver from buffering data to memory or the Receive FIFO If this bit is set during the

reception of a packet the receiver is disabled only after the packet is processed The RXEN bit is reset when the

receiver is disabled Tally counters remain active regardless of the state of this bit

Note

If this bit is set while the SONIC is currently receiving a packet both RXEN and RXDIS are set until the packet is fully received When both

RXEN and RXDIS are set RXDIS could be cleared by writing zero to it

TXP TRANSMIT PACKET(S)

Setting this bit causes the SONIC to transmit packets which have been set up in the Transmit Descriptor Area (TDA)

The SONIC loads its appropriate registers from the TDA then begins transmission The SONIC clears this bit after

any of the following conditions have occurred (1) transmission had completed (ie after the SONIC has detected

EOL e 1) (2) the Halt Transmission command (HTX) has taken effect or (3) a transmit abort condition has

occurred This condition occurs when any of the following bits in the TCR have been set EXC EXD FU or BCM

This bit must not be set if a Load CAM operation is in progress (LCAM is set) The SONIC will lock up if both bits are

set simultaneously

HTX HALT TRANSMISSION

Setting this bit halts the transmit command after the current transmission has completed TXP is reset after

transmission has halted The Current Transmit Descriptor Address (CTDA) register points to the last descriptor

transmitted The SONIC samples this bit after writing to the TXpktstatus field

DP83932C Datasheet(PDF) 28 Page - National Semiconductor (TI)