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SiriusHardware · 12th Feb 2023, 11:57 pm

You may ask, under what circumstances would you absolutely have to put code in 0F00-0F11 and / or 0FF8-0FFF?

Imagine an MK14 which has the full onboard 640 bytes of RAM.. and a VDU. You want to load and display a full screen (512 byte) graphic image on the VDU screen.

The only two 256-byte areas you can point the VDU at are 0F00-0FFF and 0B00-0BFF.

In this case you would format the Intel Hex file so that the pixel data bytes intended to go into screen RAM at 0F00-0F11 and 0FF8-0FFF are initially loaded into the I/O RAM instead.

You also load a small block shift program into I/O RAM which, when autorun, will copy the two blocks from I/O RAM to their correct locations within screen RAM, and then place the SC/MP into a forever loop so that it does not return to the monitor.

This is about the only way to display a full 512-byte screen image on an MK14 / VDU which only has onboard RAM.

12th Feb 2023, 11:57 pm	#186
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,560	Re: Yet another MK14 tape interface (ESP32). You may ask, under what circumstances would you absolutely have to put code in 0F00-0F11 and / or 0FF8-0FFF? Imagine an MK14 which has the full onboard 640 bytes of RAM.. and a VDU. You want to load and display a full screen (512 byte) graphic image on the VDU screen. The only two 256-byte areas you can point the VDU at are 0F00-0FFF and 0B00-0BFF. In this case you would format the Intel Hex file so that the pixel data bytes intended to go into screen RAM at 0F00-0F11 and 0FF8-0FFF are initially loaded into the I/O RAM instead. You also load a small block shift program into I/O RAM which, when autorun, will copy the two blocks from I/O RAM to their correct locations within screen RAM, and then place the SC/MP into a forever loop so that it does not return to the monitor. This is about the only way to display a full 512-byte screen image on an MK14 / VDU which only has onboard RAM.