SPRUJ79A November 2024 – December 2025 F29H850TU , F29H859TU-Q1
In addition to the pipeline there are a few other behaviors of the RTDMA that affect the total throughput:
A 1-cycle delay is added if the DMA is idle at any point, from the cycle at which DMA receives a trigger-interrupt to the cycle at which DMA starts the burst transfer.
A 32-bit transfer doubles throughput compared to a 16-bit transfer due to the configurable R/W port size (same number of cycles per word, but 32-bit words contain twice the data)
For example, to transfer 128 16-bit words from LDA0 RAM to LDA3 RAM, a channel can be configured to transfer 8 bursts of 16 words/burst. The transfer can take:
1 burst × [4 cycles/word × 1 word + 1 cycle/word × 15 words + 1 cycle delay] + 7 bursts × [1 cycle/word × 16 words + 1 cycle delay] = 20 + 119 = 139 cycles
If instead the channel were configured to transfer the same amount of data 32 bits at a time (the word size is configured to 32 bits), the transfer can take:
1 burst × [4 cycles/word × 1 word + 1 cycle/word × 7 words + 1 cycle delay] + 7 bursts × [1 cycle/word × 8 words + 1 cycle delay] = 12 + 63 = 75 cycles
The RTDMA module consists of a 3-stage pipeline as shown in Figure 12-3, Figure 12-4, Figure 12-5, and Figure 12-6.