CFX-3, a work in progress . . . .
Posted: 22 Jun 2018 06:11
What have we (well, Martin really), been doing lately?
Working on the 80 column emulation for MTX computers.
The background . . . .
Bill's Parallax Propeller 80 column card replacement for the MTX is a really great piece of work. It has allowed us to include 80 column card functionality with our CFX disk drive replacement board (as CFX-II, http://primrosebank.net/computers/mtx/p ... /cfxii.htm) at very little additional cost. As well as having a useable 80 column board interface, the Propeller also allows the MTX VDP output to be shadowed to drive the VGA monitor with much better quality output than from the MTX RF or composite video outputs.
Unfortunately though, some VGA monitors exhibit a noticeable amount of "noise" when displaying the 80 column card output. The "jitter" is possibly due to the Propeller using a PLL to generate its faster clock speeds, rather than allowing a higher frequency oscillator to be used. Although the 80 column display is perfectly useable, it is not perfect on some monitors.
The result . . . .
Martin wondered whether it might be possible to use a CPLD to generate VGA output from an emulated 80 column board. I found a project on the web that did just that and Martin used that as the basis for a new "80 column card" to be integrated into CFX. Leading to . . . .
CFX3 !
I am working on a CFX3 section on the website, but in the meantime, over to Martin to describe how the CFX3 VGA solution has come to pass . . . . .
regards
Dave
Working on the 80 column emulation for MTX computers.
The background . . . .
Bill's Parallax Propeller 80 column card replacement for the MTX is a really great piece of work. It has allowed us to include 80 column card functionality with our CFX disk drive replacement board (as CFX-II, http://primrosebank.net/computers/mtx/p ... /cfxii.htm) at very little additional cost. As well as having a useable 80 column board interface, the Propeller also allows the MTX VDP output to be shadowed to drive the VGA monitor with much better quality output than from the MTX RF or composite video outputs.
Unfortunately though, some VGA monitors exhibit a noticeable amount of "noise" when displaying the 80 column card output. The "jitter" is possibly due to the Propeller using a PLL to generate its faster clock speeds, rather than allowing a higher frequency oscillator to be used. Although the 80 column display is perfectly useable, it is not perfect on some monitors.
The result . . . .
Martin wondered whether it might be possible to use a CPLD to generate VGA output from an emulated 80 column board. I found a project on the web that did just that and Martin used that as the basis for a new "80 column card" to be integrated into CFX. Leading to . . . .
CFX3 !
I am working on a CFX3 section on the website, but in the meantime, over to Martin to describe how the CFX3 VGA solution has come to pass . . . . .
regards
Dave