Harlequin 128D

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The harlequin boards are a series of ZX-Spectrum recreation boards created by Superfo (And now others) based on work done by Chris Smith for his book "The ZX Spectrum ULA" (Which is an excellent read if your technically inclined by the way [Linky] ) with the addition of a disableable Kempston interface (128K versions)

There are harlequin boards for the Speccy 48, 128, and +3. The ones i have built are the 48k one and the 128D one.

These are all implemented as discrete through-hole logic for the most part (With the exception of the Video Encoder IC AD724JR which needs to be done first as its a bit of an arse if your not used to Surface mount like me.

None of these are kits for the absolute beginner, but relatively experienced builders probably wont have an issue with it.

The kit i initially got came from [bytedelight] which was the 128D one.


Harlequin 48G

This is of course the 48K version. There is a lot of similarities with the 128 version, but misses the Kempston joystick interface of the 128 version.

The rom is only compatible for a 27C128 or 27C256 or compatible, but in the case of the 27C256, the extra address line goes to J12, so you can have two different roms in the Eprom. (Personally i use 48K basic and Diagrom, and have a small switch on the back to switch between them.)

As a 48K compatible machine, this also includes Dot Crawl. However, this can be eliminated by using a SCART cable on the back. (These are easilly available on Ebay among other places)

However, because all the parts are low power rather than a 30 year old ULA, it uses a switching regulator, and *DOESNT* use the rather shonky circuit to generate 12v, -12v and -5v which is known to go bad if you look at it wrong, Its a damn sight more reliable and less power hungry.

The board is the same layout as an original 48K Machine, so can fit in a 48K case in case of the original, although if you want to use SCART, you need to cut a small piece out of the back. The Video output is composite, but these days that's a lot more convenient than the original PAL RF.

Harlequin 128D

The 128D kit is a 128K comparable by default, but can be made 128/+2A rom compatible by jumpering J18 between 2 and 3. This is useful for using the +3E Roms and a simple IDE interface to provide a hard drive (Or in my case an SD CARD interface)

The ROM is in 64k blocks in either mode, but if J18 is jumpered between 1 or 2, only the upper 32k of each 64k block is used.

Note that this board does NOT support ALLRAM mode, so booting something like CPM will not be possible, and if you implement a Floppy disk interface, DOS_BOOT will probably fail. This does not stop using the normal booting of the file "DISK" from your hard disk however.

Rom sizes should be 27256 (32K), 27512 (64K) or 29F040 (512K), although other roms with a similar pinout is acceptable. I use 29EE020 (256K) personally.

The extra wires are jumpered as follows:

Pin Ax Notes
29 A14 This is the LSB of the Rom bank from $7FFD
3 A15 This is either Jumpered to VCC (J18 1-2) for original 128K mode only, or the MSB of the rom bank from $1FFD (J18 2-3) allowing +2A/+3 rom bank mode.
2 A16 Dip switch S1, Switch 3
30 A17 (If J17 2-3) Dip Switch S1, Switch 3 (If J17 1-2), VCC. I suspect this is provide VCC for certain Eprom chips' Vpp line.
1 A18 Dip switch S1, Switch 1

As with the 48K version, its a lot more low powered than the original 128K board, and will fit in a 48k+ and 128K Toastrack case (Technically a rubber key 48K case as well, but that's a lot more difficult to use because the 128k roms expect the composite keys and its a pain in the arse to remember to use Caps-shift to negotiate the menus

Using the +3E mode

The harlequin 128 supports the +3E roms with J18 2-3 jumpered. It supports and runs the simple 8-bit IDE interface (And probably others to, but i haven't checked), for much not-having-to-arse-with-tape goodness.

Note, its likely that DOS_BOOT will always fail due to the lack of ALLRAM mode, but this will only be an issue if you have a Floppy disk interface AND some copy-protected +3 Disks to use with it. It will then fall back to trying to load "DISK" from the default drive, which does work.