Use of that bit explains why those machines have non-ASCII 64-character sets. The bit six test ensures a HALT operation gets through, which can be used to terminate a line and use no additional memory, which is helpful if you have only the base 1kb. So the hardware reuses bit 4 of the intended refresh address as the interrupt line.

The Z80 increments the refresh address for every refresh cycle, and if the instruction is of the shortest available length, the Z80 also bases an interrupt decision based on sampling the interrupt line during the refresh cycle. Parts of the next refresh address are then subverted to fetch a byte of pixels based on the latched value and the value of an internal three-bit counter. If the CPU reads an opcode from any address with the top bit set, the HALT line is not currently active and the value does not have bit six set, then the value is diverted to a latch and a NOP is supplied to the CPU. The opcode fetch on a Z80 is a two-clock-cycle memory read followed by a two-clock-cycle refresh cycle. It's one of the machines included in my current emulator so:

I'm fascinated to know how you manage to get such a display reproduced via the Tube to a BBC Micro with any degree of speed/accuracy. Neo Geo Pocket and Neo Geo Pocket Color emulator.Crj wrote:I thought the ZX81 amd ZX80 cheated by having next to no video circuitry and expecting the CPU to produce the output either via NMI or by turning the screen off while processing and enabling it only while waiting for input? Portable homebrew-emulator for Pokémon-Mini. GameBoy Advance(GBA) emulator for iPlayer only. Sega Master System and Game Gear emulator.ĭS side application used to run GBA code. Sega game Gear / Master System console emulator. Port of Snezziboy, an SNES emulator for the GBA, to the Nintendo DS platform. SEGA Master System/Game Gear/SG-1000 emulator. Port of Retrobox, multi-console emulator. Sinclair ZX Spectrum that support WiFi multiplayer.Ī Gamegear and Sega MasterSystem emulator.Įmulated game Console: SNES / Super Famicom.

Sinclair ZX Spectrum (48k model only) emulator.Įmulated Computer: Sinclair ZX Spectrum (48k model only). Re-engineer classic point and click adventure games of the 80s-90s on PC. MSX / MSX 2 / MSX2+ home computer standard emulator. You will need an R4 3DS card and a Micro SD card that you can use with the R4 and then you’re all set. I will work to create an individual page for each and every one of the emulators listed below but it will take some time as life, work and other responsibilities are front and center. These emulators give R4 3DS owners access to thousands and thousands of classic / retro / old school games for some of the best systems of yesterday.

Here’s an (in) complete list of all of the emulators available for the R4 3DS, R4i SDHC and R4 DS Cards.

Sinclair zx81 emulator