Sizif-512

Another CPLD-based ZX Spectrum clone for 48K rubber case with some sweet features.

Tech specs

• Half-sized PCB for 48K rubber case, case modifications isn't necessary
• Pentagon, Spectrum 128K and Spectrum 48K timings
• Altera EPM1270 CPLD
• Real Z80 in 3.5MHz, 7MHz (no-wait turbo) and 14MHz (turbo with wait-states) modes
• Switchable 128K / +3e-divmmc ROM
• 512K RAM
• Real AY-8910 with switchable stereo ABC/ACB/mono output
• Sega 6-button joystick input; Kempston/Sinclair modes
• Integrated DivMMC, 1x microSD socket
• PAL and RGB video out (Sega Mini-DIN/9 connector)
• Digital video out for EGA monitors
• ULAplus
• Mono covox (Pentagon standard)
• SounDrive (4-channel stereo covox)
• WiFi
• Tape input via 3.5" jack and Bluetooth
• 9-12V power supply with any polarity
• Reset and Magic buttons and , header for power button

Demonstration

Running Pentagon 128 and Spectrum 128 demos: link
Playing music from SD: link
Some photos: link

Magic button

Sizif have some configurable things which you may change at any moment and that's doesn't require reboot. To do this there is a Magic button: just hold it and press key on keyboard:

Key	Function
1	Switch to Pentagon timings (by default)
2	Switch to Spectrum 128K timings
3	Switch to Spectrum 48K timings
4	Switch to 3.5 MHz (normal) mode (by default)
5	Switch to 7 MHz (turbo) mode
6	Switch to 14 MHz (turbo) mode
7	Switch to ABC stereo (by default)
8	Switch to ACB stereo
9	Switch to mono
Q	Use default 48K BASIC
W	Use alternative 48K BASIC (OpenSE)
E	Use default 128K ROM
R	Use +3e-divmmc ROM
U	Use joystick in kempston mode (default)
I	Use joystick in sinclair mode
O	Enable all additional features: DivMMC, 512K RAM, Kempston, Covox (by default)
P	Disable all additional features
Space	Jump to #0 address (useful for ROM switching)

If you press Magic button and didn't change something, standard NMI handler 'll be called on button release.

Sega gamepad buttons

Sega gamepad support will be available starting from PCB rev.D (or Rev.C with slight modifications).

Button	Function in Kempston mode	Function in Sinclair mode
Up	Up	9
Down	Down	8
Left	Left	6
Right	Right	7
A	Button 3	N
B	Button 1	0
C	Button 2	M
X	Turbo Button 3	Turbo N
Y	Turbo Button 1	Turbo 0
Z	Turbo Button 2	Turbo M
Start	Pause	Pause
Mode	Magic/NMI	Magic/NMI

RAM

Sizif contains 512K RAM. There are two cases how to access it:

1. DivMMC enabled (SD card insert) - 128K available via 7FFDh port, 128K via DFFDh (Profi standart, most compatible with old 128K software) and 128K reserved for DivMMC.
2. No SD card present - 128K available via 7FFDh and 384K via DFFDh. Please note: ULAplus and Magic button shares one page of memory with DFFD port. If you run 512K-software, it's good idea not to use ULAplus and Magic.

Strange lines on border and creaky sounds on SD card access

It's not a bug, it's a feature ;)

WiFi module

It's possible to connect to internet with additional WiFi module.

Tested addons

• AYX-32 - OK
• BDI-ZX ver 2.0 MVcomp - OK (if SD card isn't insert)
• ZX Dandanator! Mini 2.1 - OK (if SD card isn't insert)
• ZX TSid - OK
• Multiface 128 1.00 by Steve Smith - OK (if SD card isn't insert)
• Noname +3DOS floppy controller - OK (since rev.D)
• DivIDE 5.7d - OK (if SD card isn't insert)

Changelog & current status

• Rev.A - first release. Please note the errata (in russian).
• Rev.B - abandoned. Files kept for historical reason.
• Rev.C - BDI has been removed; improved video circuit; more capable CPLD; better power circuit; add mono AY mode. Errata.
• Rev.C1 - fixed incorrect JTAG pinout; fixed incorrect silkscreen for power connector J3, tuned some circuit values. Everything seems to work. Errata.
• Rev.D:
  • added zxbus connector for in-case addons
  • added support for +3DOS floppy controller
  • added support for Sega 3/6-button gamepad
  • added PS/2 (TODO: check)
  • added Bluetooth tape input (via M18 module)
  • added alternative microSD card socket footprint
  • fixed compatibility with some keyboards
• Rev.D1: minor changes in pcb layout

Roadmap

PCB:

• create in-case addon with General Sound, TurboSound FM, SAA1099, MIDI etc

Firmware:

• add OSD for Magic button
• improve 48K/128K timings for 100% compatibility
• implement PS/2

Acknowledgments

This work is based on a lot of other projects and would hardly have been successful without them.

• Harlequin (no official link?)
• Karabas-128 (link)
• ZX Evolution (link)
• zx_ula verilog implementation (link)