Texas Instruments TM4C1294NCPDT - Figure 20-5. TX DMA Default Operation Using Descriptors

Figure 20-5. TX DMA Default Operation Using Descriptors
Start Tx DMA
(Re-)fetch next
descriptor
Write status word
to TDES0
Wait for Tx status
Transfer data from
buffer(s)
Frame xfer
complete?
Timestamp
present?
Write timestamp to
TDES6 and TDES7
Stop Tx DMA
Tx DMA suspended
No
Yes
No
Yes
No
No
Start
Yes
Ye s
Ye s
Close intermediate
descriptor
No
Yes
No
Yes
No
Poll demand
A
A
Start = 0
Error
Condition?
OWN bit
set?
Error
Condition?
Error
Condition?
Error
Condition?
TX DMA OSF Mode Operation
While in the RUN state, the transmit process can simultaneously acquire two frames without closing
the Status descriptor of the first if the OSF bit of the EMACDMAOPMODE register is set. As the
transmit process finishes transferring the first frame, it immediately polls the transmit descriptor list
June 18, 20141426
Texas Instruments-Production Data
Ethernet Controller