I think the CPU *could* do it, but why bother? Plus playing with the
state machine will be the fun part of the project for me.
The "page zero" ram stuff really doesn't apply to the Teensy, it's a
32 bit processor with a megabyte of RAM on chip. My take on the
posted code was that you just defined the values of the RAM buffer in
the C source, recompiled and reloaded using the Arduino IDE.
245's might not mind 3v3 on the data lines, but powering them from
3v3?? My data books are in the garage and I'm too lazy to go look...
73's Skip WB6YMH
On Mon, Aug 8, 2022 at 8:17 AM swguest via groups.io
<swguest@...> wrote:
Yeah, they are feature packed for sure. Kinda pricy and supply chain hobbled last I looked.
How to load to memory is probably Teensy 101 for the Teensy camp.
I havent looked at the other projects yet.
The 245's on the addr lines with 3v3 VCC on them would likely be ok.
I think the one for the data bus would likely be better served with the dual voltage 245 you mentioned a few posts back.
Given enough real estate, I'd opt for the dual voltage version for all lines.
It looks like the thing reads and presents data every time the loop is executed whether the address lines have changed or not.
He does show a CE for the data line's 245 but no reference on the uC pinout schematic, or the code to support it....hmm
Also absolute addressing puts this thing consuming zero page RAM.
PC uP do a lot of zero page R/W. I dont see any bidirectional data capabilities.
I guess to find the address where the data to be presented is in memory, follow the ANDing and bit shiting he uses to build and store in the 32 bit registers.
Interesting read but it's still vague and lacking for our purposes. I do like the compact HW design.
Looking at this code, it does make me curious what the Arduino IDE Pico module's command syntax looks like.
I scanned some googled info on the Pico's state machine and DMA features.
Very cool, I really liked what I was able to glean from my quick glance. I didnt absorb enough to figure out if those means are robust enough for our purposes.
Even though the state machine's command set was small, it might be enough to do what we want, but at 133 Mhz do we really need to unload the main uC?
