| View previous topic :: View next topic |
| Author |
Message |
ccovell
Regular
Joined: 19 Dec 2005
Posts: 100
Location: Japan
|
 Posted: Wed Nov 15, 2006 3:42 am Post subject: BRAM code |
 |
|
I'm going to try adding some BRAM-accessing code to my game, so...
Has anyone ever done any programming to interface with the BRAM area? Like, searching through it, adding/deleting files? Are there any pitfalls I should be worrying about?
_________________
http://www.chrismcovell.com |
|
| Back to top |
|
 |
David Shadoff
Regular
Joined: 10 May 2002
Posts: 83
Location: Toronto, Ontario, Canada
|
| Posted: Wed Nov 15, 2006 7:43 am Post subject: |
|
|
How are you planning on accessing it - directly, or via CDROM system card routines ?
If you are accessing it directly, you need to be in CSL slow CPU mode... but I've never tried using the system card's routines.
I also have information on the link-list format somewhere, but I'm pretty sure you can figure that out for yourself without my help...
Oh yeah, and I recall while single-stepping through games a while back that there appeared to be a write-protect latch that needed to be hit... although that didn't appear to do anything (it seemed like maybe something from a preliminary devkit maybe, which wasn't implemented in the commercial design).
Maybe Bt has done some of this stuff... |
|
| Back to top |
|
|
ccovell
Regular
Joined: 19 Dec 2005
Posts: 100
Location: Japan
|
| Posted: Wed Nov 15, 2006 2:31 pm Post subject: |
|
|
I'm going to be implementing it directly (through my own code). I know I have to switch to slow CPU mode, but I'm wondering if it's possible to do BRAM-RAM DMA transfers in that mode...?
I think I understand the format OK; I remember chatting with you on IRC as I looked at it. I think I understand the header info, and checksum (which is actually a checksubtract, since it subtracts all bytes in a save file from $0000. I'll have to refresh my memory on stuff like that.
I guess looking at how some games do it wouldn't hurt.
_________________
http://www.chrismcovell.com |
|
| Back to top |
|
|
dmichel
Admin
Joined: 04 Apr 2002
Posts: 1166
Location: France
|
| Posted: Wed Nov 15, 2006 11:57 pm Post subject: |
|
|
I don't remember who wrote it but don't we have a BRAM lib in HuC? It's written in ASM if I remember right.
_________________
David Michel |
|
| Back to top |
|
|
David Shadoff
Regular
Joined: 10 May 2002
Posts: 83
Location: Toronto, Ontario, Canada
|
| Posted: Thu Nov 16, 2006 4:39 am Post subject: |
|
|
Geez David, I think you're right.
What's really strange is... I think I wrote part of it (but I didn't work too hard at testing it). |
|
| Back to top |
|
|
nodtveidt
Elder
Joined: 27 Dec 2004
Posts: 414
Location: Isla del Encanto
|
| Posted: Thu Nov 16, 2006 1:19 pm Post subject: |
|
|
Yes, HuC has BRAM functions in the clib (since version 1.5, with some functions appearing in 3.03). I've used them for ages.
_________________
Frozen Utopia
Retro gaming was never this cool. |
|
| Back to top |
|
|
ccovell
Regular
Joined: 19 Dec 2005
Posts: 100
Location: Japan
|
| Posted: Fri Dec 08, 2006 2:59 pm Post subject: HuC BRAM libs have a bug!? |
|
|
Hi, I'm having fun (?) using the BRAM interfacing routines from HuC, but I think I've discovered a serious bug in the routines that use bm_open().
The function goes like this: | Code: | ; bm_open(char *name [bx])
; ---
; Internal function to obtain access to a named file
...
; -- compare names
cly
ldx #4
.l2: lda [_bx],Y
sxy
cmp [_si],Y
... |
But the functions bm_delete(), bm_read(), and bm_write() store the name in AX (comments mine):
| Code: | lib2_bm_delete:
__stw <_ax ;Is this for real????
jsr lib2_bm_open
bcs .out
... |
I was getting file deletion errors every time I tried, and then I noticed this mistake in the HuC Libs. Actually, several other functions also say that parameters are passed through [bx] but the functions that call them pass them through AX. Whoever actually wrote the BRAM libs might want to look into this.
_________________
http://www.chrismcovell.com |
|
| Back to top |
|
|
|
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
