Talk:ZX Interface 2

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[edit] Usage

How did the carts work? Was it necessary to enter any special commands, or did they automatically take control of the machine when inserted? --Mmartins 03:48, 9 August 2005 (UTC)

You inserted them with the computer turned off. When starting it the game ran from the cartridge ROM. // Liftarn

[edit] Joystick ports

Kempston Interface notes that the +2's joystick port was incompatible with the de facto standard (Atari 2600). However, it states the +2's joystick port was compatible with that of the Interface II. I can't find anything to support that, but it seems quite likely, and probably belongs in this article too. StuartBrady 20:10, 20 January 2006 (UTC)

The +3 (and +2a/b I assume) had the pins on the 9 pin D-sub connector wired differently from the Atari-standard. Amstrad released the SJS range (I believe) of joystics to create a lock-in. However, the internal working of the +2/+3 port (ie. the I/O address, and bit mapping) was identical to IF2 (ie. Kempston used port 31, while Sinclair used 61438 (Joystick 1) and IN 63486 (Joystick 2)).

The pin-out is as follows:

  Direction   Kempston   +2/+3

  Up             1         5
  Down           2         9
  Left           3         7
  Right          4         6
  Fire           6         4
  GND            8        2/8

--Frodet 23:11, 20 January 2006 (UTC)

So in other words, the IF2 added the new Sinclair interface (from the point of view of software) but used the Atari-standard, and the +2/+3 was incompatible with the Atari-standard, but it did still use the Sinclair interface. However, the Kempston Interface article says that a joystick was bundled with the +2, which was compatible with the IF2. Presumable, it's wrong. One thing I'm wondering is whether this also includes the grey +2, or just the black +2A? Can you damage the hardware by plugging an Atari joystick into a +2? If not, I can test this myself.

FWIW the pin-outs match what I'd already found in the Linux kernel docs. (Documentation/input/joystick-parport.txt)

--StuartBrady 01:57, 21 January 2006 (UTC)

SJS-1 (Sinclair Joystick System) sounds right [1]. --StuartBrady 02:08, 21 January 2006 (UTC)

Sorry, I all forgot about this one... :( And bear in mind that I take this from memory... :) Your first statement is true. And what the Kempston article says is:

However, when Amstrad released the ZX Spectrum +2, the computer featured built-in joystick ports and a bundled joystick that were compatible with Sinclair's ZX Interface 2 standard.

Note the plural form of "to be". :) AFAIK, both the +2, +2A/B and +3 featured the same joystick interface.

Hmm. So individually, they were not compatible, but as a whole they were. So I think the Kempston article is open to misinterpretation at the very least. --StuartBrady 23:38, 9 February 2006 (UTC)

From the +3 manual:

We recommend that you use the Sinclair SJS range of joystick(s) with the +3. Other types of joystick (e.g. Atari) will not operate directly, as their connecting plugs are wired differently.

From the pin-out, ground is the same for the two systems. Right and fire is reversed, but the rest is not shared. No harm should com from connecting an Atari joystick to a +2, but don't hold me to it. :) --Frodet 23:24, 9 February 2006 (UTC)