westfw:
Can you set up DMA to/from a set of IO pins, in a sort of traditional strobed "I've put data on these pins, and here's a signal to indicate that it's valid, so transfer that to/from memory" scheme? From brief reading of the datasheet, it looks like DMA to "ports" should be possible, but it was far less obvious whether you could get the sort of handshaking ancient devices expect...
My limited experience is with the STM32F103 stuff so may not be universal, but I would guess is typical.
The DMA controller does handshaking with the internal peripherals, e.g. does a transfer each time an ADC conversion becomes valid in ADC continuous conversion mode. Similarly one can stream data to/from GPIO ports either at a fixed rate or on events that might be handled by an interrupt, such as a pin state change. I don't think there's a way to send a value to a port and twiddle individual bits on control lines as might be needed to service an external parallel RAM all under the DMA controller.