C128 for MiSTer
Based on C64_MiSTer by sorgelig.
Based on FPGA64 by Peter Wendrich with heavy later modifications by different people.
- C128, C64 and CP/M modes.
- Chipset versions selectable from original C128 flat and newer C128 DCR.
- Supports international versions of the C128.
- Optional "pure" C64 mode (disables C128 extensions).
- C1541 read/write/format support in raw GCR mode (*.D64, *.G64).
- C1571 read/write/format support in raw GCR or MFM mode (*.D64, *.G64, *.D71, *.G71).
- C1581 read/write support (*.D81).
- Parallel IEC port for faster (~20x) loading time.
- External IEC through USER_IO port, including Fast Serial.
- VIC jailbars.
- VDC with 16k or 64k RAM and multiple colour palettes.
- Almost all C64 cartridge formats (*.CRT).
- Direct file injection (*.PRG) with detection of C128 or C64 mode.
- Dual SID with several degree of mixing 6581/8580 from stereo to mono.
- Similar to 6581 and 8580 SID filters.
- REU 16MB and GeoRAM 4MB memory expanders.
- OPL2 sound expander.
- Pause option when OSD is opened.
- 4 joysticks mode.
- RS232 with VIC-1011 and UP9600 modes either internal or through USER_IO.
- Loadable Kernal/drive ROMs.
- Special reduced border mode for 16:9 display.
- Real-time clock.
- (Experimental) Support for easy configuration of ROMs and hardware options using MRA files.
Features marked in bold are unique to the C128 core, the other features are inherited from the C64 core.
- VIC register $D030 video manipulation tricks (used in some demos, e.g. RfO part 1)
- VDC non-standard high resolution modes (e.g. VGA-like modes)
- C128 specific CRT formats
ROM files need to be provided. The ROM images will be loaded by the MiSTer on start up of the core.
There are two ways to provide the ROMs for the core: using boot ROM files, or using MRA files.
To boot using rom files, a boot0.rom and boot1.rom file need to be placed in the games/C128 directory:
boot0.romcontaining the system ROMs in this order:- ROM1: C64 Basic+C64 Kernal (16k total)
- ROM4: C128 Editor+Z80 bios+C128 Kernal (16k total)
- ROM2+3: C128 Basic (32k total)
- Character ROM: C64+C128 or ASCII+DIN (8k)
boot1.romcontaining the drive ROMs in this order:- 2x 1541 drive ROM (64k total) (repeat 4x if it's a 16k ROM image)
- 2x 1571 drive ROM (64k total)
- 2x 1581 drive ROM (64k total)
Each drive's ROM is repeated twice in boot1.rom. The first ROM is used for drive 8, the second for drive 9. This makes it possible to use different ROMs in the two drives. The 1541 ROM is 16k and needs to be repeated 4 times to fill the 64k space.
There are two optional boot roms:
boot2.romfor the optional Internal Function ROM (16 or 32k)boot3.romfor the optional External Function ROM (16 or 32k)- This is different from a cartridge (
.CRT) file, it should be a plain ROM image without the cartridge headers
- This is different from a cartridge (
(Experimental)
MRA files make it possible to create multiple ROM configurations and easily switch between them using the MiSTer interface. Each configuration will show as a separate item in the Computer cores menu. MRA files were designed for use with the arcade cores, but they also work with computer cores.
The MRA file configures all system and drive roms as well as (optionally) the internal and external function ROMs. It also contains a configuration parameter that configures the "auto" choice of the CIA, SID and VDC chips and how the Caps Lock key is configured, making it possible to quickly switch between a 1985 flat C128 and a C128DCR hardware setup, the multitude of international language versions of the C128, and even a "pure" C64 mode.
Using MRA files is the more convenient way to use multiple ROM configurations with the C128 core, but requires the user to make manual changes to the MiSTer file layout as currently the update_all script does not support MRA files for computer cores.
The following changes need to be made on the MiSTer SD-CARD or USB drive to use the MRA files:
- Move the core's
C128_XXXXXXXX.rbffile from the/_Computer/folder to a (new)/_Computer/cores/folder, - Download (some of) the
*.mrafiles from the mra directory and place them in the/_Computer/folder, - Download C128rom.zip and place that in the
/games/mame/folder,
ROMs can also be loaded from the OSD via Hardware->System ROMs and Hardware->Drive ROMs menu options. These expect a ROM file with the same layout as boot0.rom and boot1.rom as described above respectively.
The Internal Function ROM can also be loaded from the OSD via Hardware->Internal Function ROM and this is similar to using the optional boot2.rom.
- End - Run stop
- F2, F4, F6, F8, Left/Up keys automatically activate Shift key.
- F9 - š”¹ key.
- F10 - = key.
- F11 - Restore key. Also special key in AR/FC carts.
- Meta keys (Win/Apple) - C= key.
- PgUp - Tape play/pause
- PgDn - Line feed
- Print Screen - Display 40/80
- Pause/Break - No Scroll (* see note below)
- Numpad * - Help
The AltGr key (right Alt) is used to access alternative function keys. Combined with AltGr the function keys are the C128 top-row special keys. To access these functions, press and hold AltGr while pressing any of the function keys:
- AltGr+F1 - Esc
- AltGr+F2 - Alt
- AltGr+F3 - Tab
- AltGr+F4 - Caps Lock or ASCII/DIN
- AltGr+F5 - Help
- AltGr+F6 - Line feed
- AltGr+F7 - 40/80 display
- AltGr+F8 - No scroll
It is possible to access the C128 top-row cursor keys, and the numpad keys on a PC keyboard without numpad using AltGr combined with the similar keys:
- AltGr+return - Numpad enter
- AltGr+1 through 0 - Numpad 1 through 0
- AltGr+- - Numpad -
- AltGr++ - Numpad +
- AltGr+. - Numpad .
- AltGr+Cursor keys - Top-row cursor keys (** see note below)
Shift lock can be activated by pressing AltGr+Shift. This is a toggle, to release Shift lock, press the AltGr+Shift combination again.
Keys marked in blue are the keys sent when combined with AltGr.
*): The Pause/Break key acts like the No scroll key, however the Pause/Break PC key is special as it does not send a signal when it is released. To solve this, when the Pause/Break key is pressed, the No scroll key signal to the C128 is pulsed for short period. To hold No scroll on the C128 for longer, either use AltGr+F8, or quickly double press Pause/break and press any key to release No scroll.
**): When the Z80 CPU is active the top-row cursor keys become the default and AltGr selects the regular cursor keys.
If your joystick/gamepad has more than 4 buttons then you can have some limited usage of keyboard. Joystick buttons Mod1 and Mod2 adds 12 frequently used keys to skip the intros and start the game. Considering default button maps RLDU, Fire1, Fire2,Fire3, Paddle Btn, following keys are possible to enter:
- With holding Mod1: Cursor RLDU, Enter, Space, End (Run stop), Shift+End (
DLOAD"*"thenRUN) - With holding Mod2: 1, 2, 3, 4, 5, 0, Y, N
- With holding Mod1+Mod2: F1, F2, F3, F4, F5, F6, F7, F8
In the OSD->Hardware menu, internal memory size can be selected as 128K or 256K. The latter activates RAM in banks 2 and 3. C128 basic does not detect or use this memory however, so it will still show 122365 bytes free.
On a C128, the 40/80 Display switch on the keyboard selects which video mode the system will boot on, or switch to when pressing the Run stop+Restore key combination.
Since the MiSTer has a single video output, the video mode being shown needs to be selectable. The video output can be selected from the OSD menu or using the keyboard. Use the OSD->Video Output option to either make the video output follow the 40/80 Display state, or select the VIC or VDC video outputs independent of the state of the 40/80 Display switch.
In OSD->Audio & Video the VDC version, memory size and colour palette can be selected.
There are four colour palettes selectable for the VDC:
- Default: the "standard" TTL RGBI colour palette
- Analogue: the palette when using resistors to convert TTL RGBI to analogue RGB
- Monochrome: TTL monochrome monitor, with two levels of intensity
- Composite: the black and white image on the composite pin of the DB9 TTL RGBI connector
The C128's VDC has a very programmable video timing signal generator, unlike the VIC, where the video signal timing is fixed in hardware. It makes it a very flexible video chip that can generate many video modes, but it has drawbacks too. For one, it means the video output will most likely not be centered on the generated MiSTer video output, and the position can change depending on the video mode. This is an artifact of how the VDC works and not easily fixable in the MiSTer.
The VDC is clocked separately from the system clock in the C128. To have correct video sync timing, the VDC clock in the core has to run asynchronously from the master clock of the core. This causes noise on some video filter settings as the filters are clocked differently from the pixels generated by the VDC. If you experience noise on the 80 column display, change or disable the video filter.
Another known issue is that the VDC can generate video modes that the MiSTer video scaler does not correctly process. These modes can cause the scaler to stop working (it will usually recover when switching video output to the VIC) or produce extreme flickering on the video output. Be careful with VDC programs using unofficial video modes if you are sensitive to that!
To load a cartridge from the OSD menu it must be in .CRT format. C64 and C128 cartridges will be detected based on the CRT header and the core will start in the correct mode.
To convert a binary ROM image into a .CRT, the cartconv tool from Vice can be used, usually like this:
cartconv.exe -t c128 -l 0x8000 -i cart.bin -o cart.crt
The -t c128 option is needed for C128 cartridges to add the header indicating this is a C128 cartridge. Otherwise the cartridge will be detected as a C64 cartridge and the core will start up in C64 mode.
The -l 0x8000 option is needed to indicate the image should be located at address $8000. Some external ROMs might need to be located at $C000, in that case -l 0xC000 should be used.
In OSD->Hardware page you can choose Boot Cartridge or Internal Function ROM, so everytime the core is loaded, this cartridge or ROM will be loaded too.
Primary function of RS232 is emulated dial-up connection to old-fashioned BBS.
Note: Most turbo drive ROM kernals have no RS232 routines so most RS232 software don't work with these kernals!
Supported up to 4MB of memory. GeoRAM is connected if no other cart is loaded. It's automatically disabled when cart is loaded, then enabled when cart unloaded.
Supported standard 512KB, expanded 2MB with wrapping inside 512KB blocks (for compatibility) and linear 16MB size with full 16MB counter wrap. Support for REU files.
GeoRAM and REU don't conflict each other and can be both enabled.
| USER_IO | USB 3.0 name | Signal name |
|---|---|---|
| 0 | D+ | RS232 RX |
| 1 | D- | RS232 TX |
| 2 | TX- | IEC /CLK |
| 3 | GND_d | IEC /RESET |
| 4 | RX+ | IEC /DATA |
| 5 | RX- | IEC /ATN |
| 6 | TX+ | IEC /SRQ |
All signals are 3.3V LVTTL and must be properly converted to required levels!
The IEC /SRQ (USER_IO6) line is required for IEC fast serial operation with an external 1571 or 1581 drive. You will need a MiSTer user port adapter that connects the /SRQ line. Assume a MiSTer user port to IEC adapter for does not connect this line unless it is explicitly stated that it supports the C128 fast serial protocol.
RTC is PCF8583 connected to tape port. To get real time in GEOS, copy CP-CLOCK64-1.3 from supplied disk to GEOS system disk.
C1541/C1571 implementation works in raw GCR mode (D64/D71 format is converted to GCR and then back when saved), so some non-standard tracks are supported if G64/G71 file format is used. Support formatting and some copiers using raw track copy. Speed zones aren't supported (yet), but system follows the speed setting, so variable speed within a track should work. Protected disk in most cases won't work yet and still require further tuning of access times to comply with different protections.