In the "overview of DMA", Robin stated that the DMA requires both the target and source addresses before it does the work. However, in the lab sheet, there is only one address register. So, how do we store two different addresses by using only one 8-bit address register?

Is that right if only either one of the addresses is required so that in the read operation, the data at the target address is copied to the data register in the DMA, and in the write operation, the data in the data register of the DMA is copied to the target memory location. (and not from the source address to the target address)?

-- Roy Leung (roy.leung@utoronto.ca), February 20, 1999

Answers

Yes, you have the right idea.

For the purposes of this lab, you are transfering data to/from memory to a "device", and this device is the register internal to your design.

Other DMA controllers can transfer data from one region of memory to another.

-- Steven Caranci (caranci@eecg.toronto.edu), February 22, 1999.