Digi NS9215 manual Long preamble enforcement, Pure preamble enforcement, Auto detect pad enable

Models: NS9215

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E T H E R N E T C O M M U N I C A T I O N M O D U L E

MAC Configuration Register #2

Bits

Access

Mnemonic

Reset

Definition

 

 

 

 

Long preamble enforcement

D09

R/W

LONGP

0

 

 

 

 

0

Allows any length preamble (as defined in the 802.3u

 

 

 

 

 

standard).

 

 

 

 

1

The MAC allows only receive frames that contain

 

 

 

 

 

preamble fields less than 12 bytes in length.

 

 

 

 

 

D08

R/W

PUREP

0

Pure preamble enforcement

 

 

 

 

0

No preamble checking is performed

 

 

 

 

1

The MAC certifies the content of the preamble to

 

 

 

 

 

ensure that it contains 0x55 and is error-free.

 

 

 

 

 

D07

R/W

AUTOP

0

Auto detect pad enable

 

 

 

 

When set to 1, this bit causes the MAC to detect

 

 

 

 

automatically the type of transmit frame, either tagged or

 

 

 

 

untagged, by comparing the two octets following the

 

 

 

 

source address with the 0x8100 VLAN protect ID and pad

 

 

 

 

accordingly.

 

 

 

 

Note:

This bit is ignored if PADEN is set

 

 

 

 

 

 

to 0.

 

 

 

 

See “PAD operation table for transmit frames” below.

 

 

 

 

 

D06

R/W

VLANP

0

VLAN pad enable

 

 

 

 

Set to 1 to have the MAC pad all short transmit frames to

 

 

 

 

64 bytes and to append a valid CRC. This bit is used in

 

 

 

 

conjunction with auto detect pad enable (AUTOP) and

 

 

 

 

pad/CRC enable (PADEN). See “PAD operation table for

 

 

 

 

transmit frames” below. This bit is ignored if PADEN is

 

 

 

 

set to 0.

 

 

 

 

 

 

D05

R/W

PADEN

0

Pad/CRC enable

 

 

 

 

0

Short transmit frames not padded.

 

 

 

 

1

The MAC pads all short transmit frames.

 

 

 

 

This bit is used in conjunction with auto detect pad enable

 

 

 

 

(AUTOP) and VLAN pad enable (VLANP). See “PAD

 

 

 

 

operation table for transmit frames” below.

 

 

 

 

 

D04

R/W

CRCEN

0

CRC enable

 

 

 

 

0

Transmit frames presented to the MAC contain a

 

 

 

 

 

CRC.

 

 

 

 

 

1

Append a CRC to every transmit frame, whether

 

 

 

 

 

padding is required or not.

 

 

 

 

CRCEN must be set if PADEN is set to 1.

 

 

 

 

 

D03

R/W

Not used

0

Always write as 0.

 

 

 

 

 

D02

R/W

HUGE

0

Huge frame enable

 

 

 

 

0

Transmit and receive frames are limited to the MAXF

 

 

 

 

 

value in the Maximum Frame register.

 

 

 

 

1

Frames of any length are transmitted and received.

290Hardware Reference NS9215

Page 290
Image 290
Digi NS9215 Long preamble enforcement, Pure preamble enforcement, Auto detect pad enable, Vlan pad enable, Pad/CRC enable