About one byte...

[Gregounet]

Hi everyone,

once again I'm afraid I'll ask a real newbie question. And surely already been answered somewhere but wasn't able to find the answer. Please apologize...

When working on porting O2EM to a MCU, I spotted two differences in the content of the "bios" ROM between US (O2) and french (Videopac) versions:

One is "SELECT GAME" beeing replaced by "_QUEL_JEU?_" between Ox302 an 0x30C. OK.

The other one is just one byte 0x04 replaced by 0x06 at 0x2D3. Does someone knows what does this byte control ?

I don't currently have any 8048 dbg running so not able to directly look at this code...

TIA,

Grégoire

[manopac]

02d2 : be 04     mov r6,04                      ; R6 is Colour

so its apparently a different color that is used for the first letter in the text :-)
(and if you run O2EM with both Bios, you will notice that the letter on the position two (sElect vs. _Quel) is once orangish, once blueish ;-) )

[Gregounet]

Thanks: I like to understand things   

I had a hope that it was sth most important than this:

I'm fighting since many days with the Monstroth sprite in Alien Invaders. Instead of using data bytes from program memory (ROM) my port of the emulator seems to use program bytes. So this sprite is really horrible. I'm currently looking at the byte code but without any debugger and working on an Arduino through a serial link it's hard to understand the processing of the program. Must have done a mistake somewhere in my emulator.

I should start by compiling O2EM and a decent debugger on my computer to be able to compare...

[Gregounet]

I have a clue but don't succeed in using it:

Access to program data is shifted by 0x10 for the main data (shape of Monstroth) and 0x0D for Monstroth "mouth" data which will be later ANLed to main data.

0x10 is the size of the main data sets.
0x0D is the size of the "mouth" ANL elements.

But working with only a paper and a pen is laborious...