[libre-riscv-dev] Wishbone Arbiter

[whygee at f-cpu.org]

On 2020-01-27 03:40, Jacob Lifshay wrote:
> On Sun, Jan 26, 2020, 18:04 Michael Nolan <mtnolan2640 at gmail.com> 
> wrote:
> 
>> > a temporary video blip is much better than crashing due to corrupted ram.
>> 
>> I think it's not unreasonable to have the display controller be a 
>> little
>> tolerant of latency. Since the access pattern is very regular, having 
>> it
>> prefetch into a buffer of $MAXLATENCY * $PIXELFREQUENCY pixels would 
>> be
>> relatively straightforward. It would also mean the DRAM controller
>> wouldn't have to worry about initiating a refresh right before the
>> display controller initiates a read.
>> 
> 
> Yeah, I would consider having a sufficiently-sized FIFO be a basic
> requirement of the scanout engine. the only spot where it's not needed 
> is
> if the video memory was multi-ported SRAM, with one port dedicated to
> scanout, which is only feasible for really low resolutions (even 
> 640x480 is
> probably too high).

Usually, it's a good practice to buffer a whole line worth of data in 
advance,
probably during line blank or DRAM refresh.

It's good to combine video scan and refresh in a way or another because
it reduces activity on the pins, and lowers power consumption.

> Jacob
yg