Datasheet

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SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
37.5.5 Receive Buffer Queue Pointer Register
Register Name: EMAC_RBQP
Access Type: Read-write
This register points to the entry in the receive buffer queue (descriptor list) currently being used. It is written with the start location
of the receive buffer descriptor list. The lower order bits increment as buffers are used up and wrap to their original values after
either 1024 buffers or when the wrap bit of the entry is set.
Reading this register returns the location of the descriptor currently being accessed. This value increments as buffers are used.
Software should not use this register for determining where to remove received frames from the queue as it constantly changes
as new frames are received. Software should instead work its way through the buffer descriptor queue checking the used bits.
Receive buffer writes also comprise bursts of two words and, as with transmit buffer reads, it is recommended that bit 2 is always
written with zero to prevent a burst crossing a 1K boundary, in violation of section 3.6 of the AMBA specification.
• ADDR: Receive buffer queue pointer address
Written with the address of the start of the receive queue, reads as a pointer to the current buffer being used.
31 30 29 28 27 26 25 24
ADDR
23 22 21 20 19 18 17 16
ADDR
15 14 13 12 11 10 9 8
ADDR
76543210
ADDR – –