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ETHERNET COMMUNICATION MODULE
MAC Configuration Register #2
290 Hardware Reference NS9215
D09 R/W LONGP 0 Long preamble enforcement
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.
Bits Access Mnemonic Reset Definition