Members 
Search 
Help 
Register 
Login 
Home Show: Today's Messages :: Show Polls :: Message Navigator
|
   |
| PC Engine Operating System [message #659] | Thu, 08 February 2007 19:01  |
|||
| ||||
|
I've done some experiments with ISO-9660 CDFS data tracks and having the PC Engine boot from them. The next step is to create a basic OS that will load a game or command prompt from the CDFS volume. Maybe a port or something similar to OS-9 would be pretty cool. Using the BRK+operand you can have up to 255 software interrupt routines and the Arcade card would be great for swapping between programs/stacks. PCE_OS v1.0 (?) Using HuC, you would generate 'overlay' files instead of iso or pce files, create an ISO-9660 iso file with these files and other graphic/pcm/data files, and patch the first 3 sectors with the PCE security sector, load sector, and inital boot program. The system card would load a small program from sector $03 at startup, look for the _boot.os file in the CDFS table and load the 2k file. The _boot.os file sets up the system and parse through files listed in the CDFS table, storing the sector addresses for each entry into an array in memory. The _startup.sys would contain additional OS environment settings/attributes and the user file to boot(game) or the command prompt/GUI if none specified. Things to do: A PS/2 keyboard & mouse to joypad port converter and code to read the devices if plugged into the multi-tap other than port 1. Ideas? Suggestions? Comments? Hmm, is there any existing OS for the 65c02? -Rich | ||||
| ||||
| Re: PC Engine Operating System [message #660 is a reply to message #659 ] | Thu, 08 February 2007 19:02  |
||||||||
| |||||||||
The BRK/IRQ2 interrupt vector is used for ADPCM playback though, and from a coding perspective I found getting at the BRK operand was problematic in terms of efficiency. What I would do was something like this: __irq2: pha phx tsx lda $2100-offset, x .. to index the stack, where 'offset' was the offset from the stack pointer I wanted to access. But then you need to do other things like fix up the pushed PC value, etc. We could have a 128-entry table with something like this: lda #interrupt_number jsr swi : swi: pha phx asl a tax jmp [swi_dispatch, x] Then each of the 128 vectors in the swi_dispatch table point to a routine that ends with PLX/PLA/RTS. Might as well push Y while we're at it.
Good idea; using the hi-res mode would give a nice 64-character wide screen. I could shamlessly plug the software interlacing idea for a 64x60 (8x8 font) or 64x30 (8x16) character display, but it doesn't work with all TVs. 
Very doable. The PS/2 interface used for the keyboard and mouse need one output (clock) and one input (data). This could be done using the SEL and D0 pins on the joypad port. Pretty sure the signaling is standard TTL too.
I don't know of any generic ones, but the Apple and C64 computers had operating systems; with the C64 even having a graphical one (GeOS). | |||||||||
| |||||||||
| Re: PC Engine Operating System [message #661 is a reply to message #659 ] | Thu, 08 February 2007 19:02 |
|||
| ||||
One of the main 65c02 sites has a AT/XT converter board, but they use a buffer system for it. Btw, does the Huc6280 have the SOV pin like the 6502 chips and is it attached to anything? | ||||
| ||||
| Re: PC Engine Operating System [message #662 is a reply to message #659 ] | Thu, 08 February 2007 19:03 |
|||
| ||||
|
It doesn't. But if you need fast I/O response, you can map extra hardware to bits 7,6 of the data bus at a given address and do loops using BIT, which copies bits 7,6 to the N,V flags. Like this: wait: bit $1c00 ; read our hardware's status flags or whatever bmi wait .. or .. wait: bit $1c00 bvs wait This is faster than 'TST #bitmask, $1C00'. This also has the advantage of not using any registers. | ||||
| ||||
| |
| Previous Topic: | Question about the VDC latch |
| Next Topic: | PCE flashcarts |
]