Sinclair ZX80 / ZX81 Forums

That is my small ZX81 in real live:



Please note its 48 K(g) ram (room) expansion on its rear:



Siggi

PS: Full details here:
forum.tlienhard.com/phpBB3/viewtopic.php?f=3&t=775

Or maybe a real hardware vdrive connected to a PC? Set the jumper on VDRIVE2 to enable the serial mode (not the SPI mode) and use a converter from 5V TTL level (at VDRIVE2) to RS232 levels at PC. Then use a real COM port (or USB-adapter for a virtual COM port) to talk to VDRIVE2 (using a terminal e...

albertusj wrote: ↑

Tue Dec 10, 2019 10:59 am

C11 was missing! I forgot to put in one tiny 47pF capacitor. I'm such an idiot!

I also won't be happy, if my C5 would be missing ...

forum.tlienhard.com/phpBB3/viewforum.php?f=10



Siggi

A memory chip like EEPROM can replace a GAL, if the GAL performs only simple logic AND/OR/NOT functions. But a GAL can also do more complex things like timing dependent actions (has edge-triggered inputs) or can implement a state-machine (using internal latches)! Then it is not possible to replace t...

Hi Stefano thanks for that programs. Seems that the Zeddy is PDP11-compatible :mrgreen: Back in the eighties I also wrote a Hanoi program, running on my Sharp PC 1211 (so no graphics, BASIC, no recursion). But the graphic version on ZX81 looks much better. Here are some pics: IMG_4988_1024x768.JPG I...

When I ported Chopper Drop 3000 to be compiled by MCODER2, the basic program size got bigger than 16K (the generated machine code is inserted into REM in line 1). The the DFILE then moved above 32K (afaik it must be completely moved across the 32K boundary to avoid a crash). BUT THEN THE M1-LOGIC (w...

As fa as I remember I read somewhere (in this forum???) something about the developer of this rom: he told, that the printer code was added in the final development phase just before releasing the ZX80. So maybe some prototype roms contains this code, but not the released roms.

Siggi

Hi there seems to be a problem: this file contains in variable A$ the source code for an assembler file (for ASDIS). The basic program contains only REM. If the program is loaded e. g. by EO and ZX81.rom and I press RETURN, the listing is written to screen and the Zeddy is alive. If the program is l...

Hi Greg this is not a real "inkey" function like in BASIC. The BASIC inkey$ function reads the keyboard "on the fly" and does not wait for a key to be pressed. But this mc stays inside a loop (and does not return) if no key is pressed: @Again Call Keyboard ;Call ROM scan keybd. INC L ;Check for no k...

Connecting a joystick directly to the keyboard lines will overload the Z80 addressbus (driving the keyboard lines), because the capacitive load of the long cable to the external joystick is too high. At least some additional components (transistors or driver ICs) are necessary to drive this long cab...