E F E c o n f i g u r a t i o n

Bits

Access

Mnemonic

Reset

Description

 

 

 

 

 

D24

R/W

ERXBAD

0

Accept bad receive packets

 

 

 

 

When set to 1, allows the MAC to accept packets

 

 

 

 

received in error. Bad receive packets include those

 

 

 

 

packets with CRC errors, alignment errors, and

 

 

 

 

dribble errors.

 

 

 

 

The ERXBAD bit is used primarily for debugging.

 

 

 

 

 

D23

R/W

ETX

0

Enable transmit FIFO

 

 

 

 

0 Disables outbound data flow and resets the

 

 

 

 

 

FIFO

 

 

 

 

1 Enables outbound data flow

 

 

 

 

Set to 1 to allow data to be written to the TX FIFO.

 

 

 

 

Clear to reset the transmit side FIFO.

 

 

 

 

 

D22

R/W

ETXDMA

0

Enable transmit DMA

 

 

 

 

0 Disables outbound DMA data request

 

 

 

 

1 Enables outbound DMA data request

 

 

 

 

Set to 1 to allow the EFE module to issue transmit

 

 

 

 

data move requests to the DMA controller.

 

 

 

 

Clear this bit to temporarily stall transmit side

 

 

 

 

Ethernet DMA.

 

 

 

 

Do not set this bit when operating the Ethernet

 

 

 

 

receiver in interrupt service mode.

 

 

 

 

 

D21:20

R/W

ETXWM

0

Transmit FIFO water mark before transmit start

 

 

 

 

00

25% FIFO full

 

 

 

 

01

50% FIFO full

 

 

 

 

10

75% FIFO full

 

 

 

 

11

Reserved

 

 

 

 

Identifies the minimum number of bytes required in

 

 

 

 

the transmit FIFO to initiate packet transmission. A

larger watermark setting increases transmit packet latency, allowing for more slack in the memory system FIFO fill rate.

Note that packet transmission can also be initiated using DMA (see "Ethernet transmitter considerations" on page 144) and the FIFO Data register (see "Ethernet FIFO Data register" on page 167).

Table 53: Ethernet General Control register bit definition

1 6 0

N S 7 5 2 0 H a r d w a r e R e f e r e n c e , R e v . D 0 3 / 2 0 0 6

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Image 174
Digi NS7520 Accept bad receive packets, Enable transmit Fifo, Enable transmit DMA, Receiver in interrupt service mode