Datasheet

556
SAM7X Series [DATASHEET]
6120K–ATARM–11-Feb-14
37.5.6 Transmit Buffer Queue Pointer Register
Register Name: EMAC_TBQP
Access Type: Read-write
This register points to the entry in the transmit buffer queue (descriptor list) currently being used. It is written with the start location
of the transmit 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. This register can only be written when bit 3 in the transmit status reg-
ister is low.
As transmit buffer reads consist of bursts of two words, 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: Transmit buffer queue pointer address
Written with the address of the start of the transmit queue, reads as a pointer to the first buffer of the frame being transmitted or
about to be transmitted.
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 – –