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IDT Ethernet Interfaces
Ethernet Medium Access Controller (MAC)
79RC32438 User Reference Manual
11 - 24
November 4, 2002
Notes
FLC
Description:
Frame Length Checking.
When this bit is set to 1, both transmit and receive frame lengths are
compared to the length/type field. If the length/type field represents a length, a check is per-
formed. When this bit is set to 0, Frame Length Checking is disabled.
Initial Value:
0x0
Read Value:
Status
Write Effect:
Modify Value
HFE
Description:
Huge Frame Enable.
When this bit is set to 1, frames of any length may be transmitted and
received. When this bit is set to 0, transmission is aborted after the length in ETH[0|1]MAXF has
been reached and the remainder of the frame is discarded.
Initial Value:
0x0
Read Value:
Status
Write Effect:
Modify Value
DC
Description:
Delayed CRC.
When this bit is set to 1, a four byte proprietary header exists on the front of all
IEEE 802.3 frames. CRCs are not computed over the proprietary header. Thus, when this bit is
set to 1, CRC calculations are delayed by four bytes. When this bit is set to 0, Delayed CRC is
disabled.
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
CEN
Description:
CRC Enable.
When this bit is set to 1, the MAC pads all short frames and appends a CRC to
every frame. When this bit is cleared to 0, frames passed to the MAC are assumed to have a
valid length and CRC (that is, these operations are performed in software). Refer to Table 11.4.
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
PE
Description:
Pad Enable.
When this bit is set to 1, the MAC pads short transmit frames and computes and
appends a CRC on all transmit frames. When this bit is set to 0, frames are padded prior to being
passed to the MAC (i.e., padding operation is performed by software). Refer to Table 11.4.
Initial Value:
0x0
Read Value:
Previous value written
Write Effect:
Modify value
VPE
Description:
VLAN
Pad Enable.
When this bit is set to 1 and padding is enabled, short transmit frames are
padded to 64 bytes. If padding is enabled and this bit is cleared to 0, short transmit frames are
padded to 60 bytes. Refer to Table 11.4.
Initial Value:
0x0