MODE=NORMAL
DMA Channel 0 Transfer Count
| COUNT | 28-bit transfer count (256 million transfers maximum). Program the number of bus transfers a channel will perform before halting. Note that, if transfers are larger than one byte in size, this is not equal to the number of bytes transferred (see CTRL_DATA_SIZE). When the channel is active, reading this register shows the number of transfers remaining, updating automatically each time a write transfer completes. Writing this register sets the RELOAD value for the transfer counter. Each time this channel is triggered, the RELOAD value is copied into the live transfer counter. The channel can be started multiple times, and will perform the same number of transfers each time, as programmed by most recent write. The RELOAD value can be observed at CHx_DBG_TCR. If TRANS_COUNT is used as a trigger, the written value is used immediately as the length of the new transfer sequence, as well as being written to RELOAD. |
| MODE | When MODE is 0x0, the transfer count decrements with each transfer until 0, and then the channel triggers the next channel indicated by CTRL_CHAIN_TO. When MODE is 0x1, the transfer count decrements with each transfer until 0, and then the channel re-triggers itself, in addition to the trigger indicated by CTRL_CHAIN_TO. This is useful for e.g. an endless ring-buffer DMA with periodic interrupts. When MODE is 0xf, the transfer count does not decrement. The DMA channel performs an endless sequence of transfers, never triggering other channels or raising interrupts, until an ABORT is raised. All other values are reserved. 0 (NORMAL): undefined 1 (TRIGGER_SELF): undefined 15 (ENDLESS): undefined |