#37170 - demitri - Tue Mar 08, 2005 1:22 pm
Hey Everyone,
I'm having some issues with DMA. I'm trying to place some pointers in a specific place in memory. I can, however, create the pointers, but when I attempt to place an int into those memory addresses. I cannot find the value. here is my code. If you have any ideas. please let me know. thanks.
| Code: |
#define VariableData ((unsigned short*)0x8000000)
unsigned short* cdph_h= VariableData +4;
unsigned short* cdph_t = VariableData + 5;
unsigned short* cdph_s = VariableData + 6;
unsigned short* cdph_dt = VariableData + 7;
unsigned short* cdph_dh = VariableData + 8;
unsigned short* tdph_h = VariableData + 9;
unsigned short* tdph_t = VariableData + 10;
unsigned short* tdph_s = VariableData + 11;
unsigned short* tdph_dt = VariableData + 12;
unsigned short* tdph_dh = VariableData + 13;
unsigned short* pdph_h = VariableData + 14;
unsigned short* pdph_t = VariableData + 15;
unsigned short* pdph_s = VariableData + 16;
unsigned short* pdph_dt = VariableData + 17;
unsigned short* pdph_dh = VariableData + 18;
.
.
.
int main (void){
*cdph_h = 1;
*cdph_t = 2;
|
etc. thanks
#37184 - poslundc - Tue Mar 08, 2005 5:45 pm
The 0x08000000 region of memory points to ROM data, which is read-only.
Dan.
#37331 - tepples - Thu Mar 10, 2005 3:37 pm
Whether the data in the ROM section of the address map is read-only depends on your cart. For official Game Paks and EFA flash carts, it is read-only. For most other flash carts, it is read-only unless you execute a specific unlocking sequence, but that's a bit advanced for most of us, and given the quality reputation of Chinese no-name electronics, I wouldn't recommend repeated flash writes.
Use EWRAM instead, (EDIT) unless you need persistence. In that case, use SRAM.
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Last edited by tepples on Fri Mar 11, 2005 4:14 pm; edited 1 time in total
#37343 - poslundc - Thu Mar 10, 2005 5:55 pm
| tepples wrote: |
| Whether the data in the ROM section of the address map is read-only depends on your cart. |
So long as we're referring to it as the ROM section, though, I'm inclined to think of it primarily as read-only. ;)
Dan.
#37358 - demitri - Thu Mar 10, 2005 8:39 pm
Fair Enough.
Thanks.
So i''ve moved my thinking. Now i'm goin to write to EEPROM on the cart. so now i just have to write the functions to do so. Does anyone know of some working code i may have a look at. I have viewed the code in the post named "EEPROM Troubles". anyone know of any other code. I haven't tried that code yet. I'm in the process of doing so. Regardless, many sources are always a better learning tool... So if anyone knows of any please let me know. Thank again!
-Demitri
#37401 - FluBBa - Fri Mar 11, 2005 11:49 am
It's way easier to start out with just SRAM, starts at 0x0E00000 and ends at 0x0E007FFF.
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#37440 - demitri - Fri Mar 11, 2005 6:33 pm
I would use sram, but i can't. I'm actually going to write to EEPROM within a microchip PIC. thus, i need to write the EEPROM read/write protocol...
-demitri
thanks for the info though.
#37478 - ymalik - Fri Mar 11, 2005 10:21 pm
What is the minimum amount the DMA can copy and still be fast?
#37482 - poslundc - Fri Mar 11, 2005 11:04 pm
| ymalik wrote: |
| What is the minimum amount the DMA can copy and still be fast? |
It depends what memory regions you are copying to/from, but as a rule of thumb I usually don't bother to use DMA for copies under 32 bytes.
At that small an amount, of course, the speed advantage of one method or the other approaches insignificance, so I defer to software copying, which is generally less likely to interfere with other GBA systems and is easier to read and debug.
Dan.
#37492 - ymalik - Sat Mar 12, 2005 1:29 am
| poslundc wrote: |
It depends what memory regions you are copying to/from, but as a rule of thumb I usually don't bother to use DMA for copies under 32 bytes.
|
Much thanks.
I'm going to be copying either from ROM to VRAM, ROM to IRAM, IRAM to VRAM, ROM to WRAM, or WRAM to VRAM. Of course, I won't use all combinations: based on the size of the data from the ROM, I'm still deciding whether to use WRAM or IRAM for a temporary buffer.
#37537 - gb_feedback - Sat Mar 12, 2005 9:04 pm
| Quote: |
| I would use sram, but i can't. I'm actually going to write to EEPROM within a microchip PIC. thus, i need to write the EEPROM read/write protocol... |
That's a bit of a thread stopper. Do you mean that the EEPROM you want is in a PIC which is in a Cart? Or that you are going to use a PIC to write to the EEPROM on an official cart, or a commercial cart which uses EEPROM? This leaves me very confused.
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#37751 - demitri - Tue Mar 15, 2005 8:38 pm
yes... hahah. ok sorry.
The EEPROM is in a PIC which is in a Cartridge. its a home-made pcb board/cartridge, which contains the PIC. Internal to the PIC lives an EEPROM which i need to write to.
I have found the protocol i was looking for, and it doesn't freeze up the gameboy. well using an EZFA cartridge. the home-made cart is being built soon.
Thanks for everyone's input.
-demitri