UM10503
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User manual
Rev. 1.3 — 6 July 2012
692 of 1269
NXP Semiconductors
UM10503
Chapter 26: LPC43xx Ethernet
26.6.8 MAC VLAN tag register
The VLAN Tag register contains the IEEE 802.1Q VLAN Tag to identify the VLAN frames.
The MAC compares the 13th and 14th bytes of the receiving frame (Length/Type) with
0x8100, and the following 2 bytes are compared with the VLAN tag; if a match occurs, it
sets the received VLAN bit in the receive frame status. The legal length of the frame is
increased from 1518 bytes to 1522 bytes.
If the VLAN Tag register is configured to be double-synchronized to the MII clock domain,
then consecutive writes to these register should be performed only after at least 4 clock
cycles in the destination clock domain.
26.6.9 MAC Debug register
This debug register gives the status of all the main modules of the transmit and receive
data-paths and the FIFOs. An all-zero status indicates that the MAC core is in idle state
(and FIFOs are empty) and no activity is going on in the data-paths.
7
DZPQ
Disable Zero-Quanta Pause
When set, this bit disables the automatic generation of Zero-Quanta Pause Control
frames on the deassertion of the flow-control signal from the FIFO layer. When this bit
is reset, normal operation with automatic Zero-Quanta Pause Control frame
generation is enabled.
0
R/W
15:8
-
Reserved
0
RO
31:16
PT
Pause time
This field holds the value to be used in the Pause Time field in the transmit control
frame. If the Pause Time bits is configured to be double-synchronized to the MII clock
domain, then consecutive writes to this register should be performed only after at
least 4 clock cycles in the destination clock domain.
0x000
0
R/W
Table 539. MAC Flow control register (MAC_FLOW_CTRL, address 0x4001 0018) bit description
…continued
Bit
Symbol
Description
Reset
value
Access
Table 540. MAC VLAN tag register (MAC_VLAN_TAG, address 0x4001 01C) bit description
Bit
Symbol
Description
Reset
value
Access
15:0
VL
VLAN Tag Identifier for Receive Frames
This contains the 802.1Q VLAN tag to identify VLAN frames, and is compared to the
fifteenth and sixteenth bytes of the frames being received for VLAN frames.
Bits[15:13] are the User Priority, Bit[12] is the Canonical Format Indicator (CFI) and
bits[11:0] are the VLAN tag’s VLAN Identifier (VID) field. When the ETV bit is set, only
the VID (Bits[11:0]) is used for comparison.
If VL (VL[11:0] if ETV is set) is all zeros, the MAC does not check the fifteenth and
sixteenth bytes for VLAN tag comparison, and declares all frames with a Type field
value of 0x8100 to be VLAN frames.
0x000
0
R/W
16
ETV
Enable 12-Bit VLAN Tag Comparison
When this bit is set, a 12-bit VLAN identifier, rather than the complete 16-bit VLAN
tag, is used for comparison and filtering. Bits[11:0] of the VLAN tag are compared with
the corresponding field in the received VLAN-tagged frame.
When this bit is reset, all 16 bits of the received VLAN frame’s fifteenth and sixteenth
bytes are used for comparison.
0
R/W
31:17
-
Reserved
0x000
0
RO