SPRUII0F May 2019 – June 2024 TMS320F28384D , TMS320F28384D-Q1 , TMS320F28384S , TMS320F28384S-Q1 , TMS320F28386D , TMS320F28386D-Q1 , TMS320F28386S , TMS320F28386S-Q1 , TMS320F28388D , TMS320F28388S
The Ethernet module supports two Transmit queues. The number of Tx channels is equal to the number of Tx queues. The different scheduling algorithms are detailed below. The algorithm is chosen by the SCHALG field setting of the MTL_Operation mode register.
Fixed Priority Scheme: The fixed priority scheme is the default priority scheme for the DMA channels. In fixed priority scheme, the channel with highest priority always wins the arbitration when the channel requests the bus.
Priority Level | Channel |
---|---|
0 (low) | Channel 0 |
1 | Channel 1 |
Weighted Strict Priority Scheme: In Weighted Strict Priority (WSP), the weight corresponds to the number of burst transfers given to a channel in one arbitration cycle. The unused burst transfers of one or more channels are reallocated based on the priority. The channel with highest priority gets the unused burst transfer time before the transfer time is allocated to a channel with next highest priority.
Weighted Round Robin Scheme (defaulted by design): The channel priorities are fixed. Channel 1 has the highest priority and Channel 0 has the lowest priority. When a channel uses the allocated burst transfers, the channel with next lower priority is processed. After processing the allocated bandwidth of all channels that had packets to transmit, any unused burst transfer time is allocated to the channel of the highest priority (if required), and then next highest priority (if required), and so on. It is suggested to program the TCW field of the DMA_CHn_Tx_Control Register with nonzero weights, if this scheme is chosen.
TCW Field | Transmit Channel Weight |
---|---|
000 | 1 |
001 | 2 |
010 | 3 |
011 | 4 |
100 | 5 |
101 | 6 |
110 | 7 |
111 | 8 |