Part 1 – an overview, and some details of the On-Screen Display
Both the OneChipMSX and PC Engine cores on this site make use the ZPUFlex processor to provide a bootstrap, control and OSD module. Let’s take a closer look at this control module:
The control module needs to provide the following services:
- Load a ROM from SD card (holding the host core off the SD card during the process, if necessary)
- Provide an On-Screen Display, toggled by the F12 key. The on-screen display must be generated in a form that can be merged with the host core’s video output.
- Prevent keystrokes reaching the host core while the OSD is displayed
- Allow various options to be set, and the settings to be read by the host core
- Perform any high-level peripheral translation (keyboard-based gamepad emulation for the PC Engine core, mouse emulation for the OneChipMSX)