xxx Posted September 4, 2023 Share Posted September 4, 2023 very little seems to be written about this system. i was wondering where the user definable characters were stored in ram? so i could change them with a poke, instead of using the cumbersome seteg command. i tried running a program to peek the memory from -32767 to 32767, looking for 10 identical numbers that i had written in seteg, to no avail. any help would be appreciated Quote Link to comment Share on other sites More sharing options...
manopac Posted September 4, 2023 Share Posted September 4, 2023 they are not 🙂 thats why you cant find them in ram ... seteg is actually a command in the G7400 Basic (16KB, written in Z80 code) that instructs the cart stuck into the G7400 (2 KB, written in 8048h code) to redefine a character on the EF9340+EF9341 chips (special chips in the G7400 not present in the G7000, that were also used in various teletext systems) - so no simple poke to set the characters 🙂 you could disassemble the C7420 Rom Source to see what exactly seteg is doing and it might be possible to write a machine language program in Z80 code you could poke into memory and run - but I doubt it would give you a speed advantage over seteg ... also - not really worth scanning the memory from -32767 to 32767 - the C7420 has only 16KB of ram 🙂 1 Quote Link to comment Share on other sites More sharing options...
xxx Posted September 5, 2023 Author Share Posted September 5, 2023 (edited) *deleted Edited September 5, 2023 by xxx 1 Quote Link to comment Share on other sites More sharing options...
xxx Posted September 5, 2023 Author Share Posted September 5, 2023 (edited) 14 hours ago, manopac said: they are not 🙂 thats why you cant find them in ram ... seteg is actually a command in the G7400 Basic (16KB, written in Z80 code) that instructs the cart stuck into the G7400 (2 KB, written in 8048h code) to redefine a character on the EF9340+EF9341 chips (special chips in the G7400 not present in the G7000, that were also used in various teletext systems) - so no simple poke to set the characters 🙂 you could disassemble the C7420 Rom Source to see what exactly seteg is doing and it might be possible to write a machine language program in Z80 code you could poke into memory and run - but I doubt it would give you a speed advantage over seteg ... also - not really worth scanning the memory from -32767 to 32767 - the C7420 has only 16KB of ram 🙂 is there an annotated rom disassembly somewhere online? i actually wrote a program that sticks numbers straight into the basic code but i would like to do it the other way Edited September 5, 2023 by xxx Quote Link to comment Share on other sites More sharing options...
manopac Posted September 5, 2023 Share Posted September 5, 2023 not to my knowledge - I remember annotating the G7400 OS specific parts in the OS Rom, but never the two Roms for the C7420 ... Quote Link to comment Share on other sites More sharing options...
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