
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
Clock synchronization
276
Hardware Reference NS9215
Multicast address
filtering example
2
To accept multicast packets with destination addresses in the range of
0x01_00_5E_00_00_00 to 0x01_00_5E_00_00_0f using entry 4, the registers are set as
shown:
Notes
If any of the address filter entries are enabled, the SAL must be set up to
accept all multicast packets by setting the PRM bit in the Station Address Filter
register.
Runt packets that are less than 6 bytes, and therefore do not have a valid
destination address, are automatically discarded by the multicast address
filtering logic.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
C l o c k s y n c h r o n i z a t i o n
The multicast filtering logic resides in the RX CLK domain, but all of the registers
are controlled in the AHB clock domain. To provide traditional dual-rank clock
synchronization flops for each bit of the five Multicast Address Filter registers
consumes a large amount of gates. Therefore, the logic is designed such that only
the MFILTEN register bits are synchronized and when these bits are cleared, changes
in the other register values are not seen at the input of any internal flops in the RX
CLK domain.
Writing to other
registers
Use these steps to dynamically write to any of the other Multicast Address Filter
registers:
1
Clear the enable bit in the MFILTEN register for the address filter you want to
change.
2
Update the address filter registers for the disable filter.
3
Set the enable bit for the address filter that was just changed.
If the address filters are changed only when the
RX_WR
logic is reset or not
processing frames, as recommended, the address filter registers can be updated
without using this procedure.
Register
Value
Function
MFILTEN
0x10
Enable entry 4
MFILTL4
0x5E_00_00_00
Lower 32 bits of multicast address
MFILTH4
0x01_00
Upper 16 bits of multicast address
MCMSKL4
0xFFFF_FFF0
Include only bits [31:04] of the lower 32 bits of the
multicast address in the comparison.
MCMSKH4
0xFFFF
Include all of the upper 16 bits of the multicast address
in the comparison
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Страница 354: ...E X T E R N A L D M A DMA Peripheral Chip Select register 354 Hardware Reference NS9215...
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Страница 384: ...I O HU B M OD UL E Module Direct Mode TX Data Last FIFO 384 Hardware Reference NS9215 31 March 2008...
Страница 414: ...S E R I A L C ON T RO L M O D U L E U ART UART Modem Status register 414 Hardware Reference NS9215...
Страница 446: ...S E R I A L C ON T RO L M O D U L E S PI SPI timing characteristics 446 Hardware Reference NS9215...
Страница 472: ...R E A L TI M E C L O C K M O D U L E General Status register 472 Hardware Reference NS9215...
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