[[File:PlayCity.jpg|thumb|320px|]]
==Introduction==
The PlayCity is a CPC expansion with previously known as the next CTC-AY.It has been released on April 2014 with these features:
* 6 audio channels sound with programmable frequency (stereo line out and speaker mono mix in).
* 4 counter/timer channels for programmable interrupt (including NMI).
* The LIGHT PEN/GUN connector.
[[File==Technical description==The board main feature is the Zilog Z80 Counter Timer Circuit, the best friend of the Zilog Z80 CPU.The CTC is linked to the CPU to allow it to manage vectorized interrupt (IM2) and handling triggered events.Programmers can only get benefit of that to save CPU time and make complex programs more easy to achieve.I can only invite them to read the Zilog CTC data-sheet for more informations. (it's really easy to use) Because the CPC expansion port have some interesting signals on it, it had been a shame to not use them.* CTC channel 0 is a programable audio clock generator. i.e. allow to replay ST or ZX sound on a CPC using AUDIO pin.* CTC channel 1 is linked to the CURSOR pin and triggered by the NMI pin. Allow accurate hi priority rasters effects.* CTC channel 2 and 3 are linked together and offers 2x8bit or 1x16bit user purpose timer or counter. ADDER is the ADDress decodER part of the board. It manage all the ICs.Because ports are direct access to the hardware, it's really fast.* CTC channels: #F880, 81, 82, 83* Audio right: #F884, #F984* Audio left: #F888, #F988* Soft reset:PlayCity#F8FF At end, the LIGHTPEN pin is rooted to a 4 pins connector for plugging compatible hardware through an adapter.jpg]]
==Hardware Installation==
Used by the standard BIOS functions
'''MC_BOOT_PROGRAM''' and '''MC_START_PROGRAM''' (vectors $BD13 and $BD16), in particular a peripheral that generates interrupts. Also used by [[FutureOS]].
The PlayCity board use this feature to be sure that the CTC and YMZs circuits are properly reseted reset before using them.
== Light Pen/Gun connector ==
For making it easier to adapt Light Pens/Guns from other systems or new ones, we added a 4 pins -pin connector to the board. The connections are labeled in the board as VCC (+5V), TR (Trigger or D7), LS (Light Sensor) and GND. Trigger (TR) = Request via output to port &FBFE. Light Sensor (LS) = CRTC Light Pen input.
Making the system compatible with [[Amstrad_Magnum_Phaser|Amstrad Magnum Phaser]] games, the most accuracy light gun system for CPC.
==Counter/Timer Circuit==
===InformationsInformation===
The Z84C30 has four independently programmable counter/timer channels interfaced directly with the Z80 CPU. You can get full information in the CTC datasheet ([[File:Z80ctc.pdf]]).
Used as a counter, it's synchronized with the CRTC CURSOR signal, generating a smooth high priority rasters interrupt. Used as a
timer (prescaler set to 256), it's its 15.625 kHz signal is scanline-synchronized. That means the time constant is the number of
scanlines to wait before to send an NMI.
====Channel 2/3 ($F882/$F883)====
The channels 2 and 3 are dedicated to general purpose usages. Yes, it's for you! The input for the trigger (TRG2) is the 4 MHz
system clock. The output (ZC/TO2) is linked to the trigger for the channel 3 (TRG3). They can be used as 2x 8-bit or 1x 16-bit
counter/timer. They generate normal interrupts and allow to use using the Z80 vector interrupt (mode 2) too.
===Coding examples===
Each channel is programmed with two bytes; a third is necessary when interrupts are enabled. Once started, the CTC countdown
Don't forget to use RETN for NMI handlers as well as RETI for normal interrupt handlers. In other case, the Z80 CPU will not
aknowledge the next interrupt properly.
==Audio Channels==
===Informations===
the frequency by reprograming the CTC Channel 0.
===YMZ294 Registers===
They are exactly the same than the [[PSG]], only remember there is not PSG I/O registers ($0E-$0F) in the YMZ. The registers are write only.
===Coding Examples===
==PlayCity coding tips==
Interesting tips or "magic tricks" using the board should be documented here. If the code is long, you must put in other wiki page and link it here.
===PlayCity detection===
We are going to use the NMI interrupt generator to check if our program is running in a CPC with a PlayCity board.
OR IXL ; (2)
JR NZ,.loop_wait_scanlines_ix ; (2/3)
; Total loop --> 16 * (IY IX - 1) + 15
RET ; (3)
; Total Routine --> 64 * SCANLINES
DEFS 1
</pre>
===PlayCity detection (alternative)===
Faster and shorter, but untested or not working on all CPC.
<pre>
;=========================
; PlayCity check
; If it's present, A=1
; Otherwise, A=0
;-------------------------
;
;=========================
macro PlaycityDetection
; Code for NMI management
ld a,#3c ; inc a
ld (#66),a
ld hl,#45ed ; (inverted) opcodes for retn
ld (#67),hl
; If a Playcity is present, the code generates a NMI then stops the counter.
ld bc,#F881 ; 3 NOPs CTC channel 1
ld hl,%00010111*256 + 2 ; 3 NOPs A NMI every 8 NOPs
out (c),h ; 4 NOPs
out (c),l ; 4 NOPs
ld a,0 ; 2 NOPs A is set to 0. If a CTC is present, it will be INCed by the INTerruption code
inc hl ; 2 NOPs L=3 => Stop CTC channel
nop ; 1 NOPs
out (c),l ; 4 NOPs <- If a Playcity is plugged, a NMI should be raised during this opcode
mend
</pre>
==Downloads==
In [[File:playcity_examples.zip]], you will find more examples with full sources of using the CTC, a customized arkos player that let you play songs using an external YMZ and the ReSeT party demo disk that includes a CPC version of the PT3 Turbo Sound player (6 channels song format).
Another example, in [[File:test_sfx.zip]] you will find a 3 channels SFX player, you can choose the sound chip to be used by the player.
== Software Supporting PlayCity ==
*[[Software_Supporting_PlayCity|List of software supporting the board.]] [[Category:FutureOS]][[Category:Music and sound]][[Category:Peripherals]] Website: [http://centpourcent.net centpourcent.net]