ZXDS is an emulator of Sinclair ZX Spectrum for Nintendo DS, written by Patrik Rak. It is steadily reaching a mature stage of development, and it already has some noteworthy features, like accurate emulation of Spectrum 48k, 128k and Pentagon models (including sound), or support for TAP/TZX/PZX tape files, TRD/SCL disk files and RZX playback files.

Changes:

ZXDS 1.2.0 (19.2.2014)

+ Proper Spectrum +2/+2A/+3 emulation, including contention and everything.
+ Support for +3DOS 3″ DSK/EDSK disks, including autoboot and disk browser.
+ TR-DOS formatting now also works for all possible disk format types.
+ File and directory name filtering is now available in file requester.
+ All keyboard keys are now sticky whenever the emulation is paused.
* In load requester, L/R+Y now shows the other medium than Y does.
* Button input in file viewer can be now toggled with icon or L/R+X and Pause.
* Full size TR-DOS disks are now always treated as double track and double sided.
* Alternate save/load directories now work better and even with filter enabled.
* Various internal changes (ROM deltas, SZX +3DOS support, plus model stats, media icon).
* Minor bugfixes (FTP files caching, hex decoding, TR-DOS BASIC start line).

http://zxds.raxoft.cz/