What access time is it possible to choose memory with, to load a background picture? And farther to work in the character mode.
p.s. Memory will be filled an external comptroller.
It's not about access time. If you fill the memory from an external controller, there will be a lot of logic between the memory and the Propeller and that will swamp any access time issues. The main issue will be how to access the memory contents from the Propeller with the limited number of I/O pins available. VGA requires at least 8 I/O pins. The programming and EEPROM ports require 4 I/O pins. That leaves 20 assuming you're doing nothing else. A 1MB memory normally requires 20 bits of address plus 8 bits for a data bus plus 3 or 4 control lines. You don't have that many available which means you need to multiplex some of them. Have a look at the Hydra Xtreme 512K Memory Expansion Card for one example of using an external controller for external memory for a Propeller.
It about access time. With memory I organize the interface of exchange of Propeller on FPGA. Whether this chip is suitable for realization, so-called, converter of Rs-232 -> VGA?
Thus a background picture is loaded in separate memory and not·changed during work, but text strings loaded in other memory and can will change during work.
If calculation time of output data to display: 1024x768 = 786432 bytes x 75Hz = 58982400 = 59Mb per second. ????? Propeller is not die?
I don't understand from your diagram what you expect the Propeller to do other than simple timing for the VGA sync pulses and the pixel timing. It looks the Propeller simply clocks the FPGA, once for each pixel. I don't see why you can't simply connect the FPGA output through a resistor ladder DAC (like the Propeller VGA circuit uses), then to the display. For that matter, the FPGA could even do the pixel clocking and sync pulses and you wouldn't need the Propeller at all.
If you want to mix text and background using the Propeller as the primary controller, then the text memory and the rendering of the text would need to be on the Propeller which is easily doable with the existing internal memory. You would need the external memory for the background and the FPGA could do the combining of the pixel data from the Propeller with the background memory bytes to produce the digital pixel stream. The Propeller could provide the pixel clock as well as signals to set the initial pixel address during the horizontal and vertical retrace times.
Comments
Thus a background picture is loaded in separate memory and not·changed during work, but text strings loaded in other memory and can will change during work.
If calculation time of output data to display: 1024x768 = 786432 bytes x 75Hz = 58982400 = 59Mb per second. ????? Propeller is not die?
If you want to mix text and background using the Propeller as the primary controller, then the text memory and the rendering of the text would need to be on the Propeller which is easily doable with the existing internal memory. You would need the external memory for the background and the FPGA could do the combining of the pixel data from the Propeller with the background memory bytes to produce the digital pixel stream. The Propeller could provide the pixel clock as well as signals to set the initial pixel address during the horizontal and vertical retrace times.
http://www.multilabs.net/ezVGA.html
this chip can only control a resolution of 320 x 240 at 64 colors. That's what a Propeller can do better.