Changes
/* Links */
==Hardware Installation==
* Power OFF your Amstrad / Schneider CPC.
* Attach the PlayCity board to one free MotherX4 slogslot.* Turn ON your computer, and enjoy! (if a grey screen appear, turn off your computer and check the connections)
==Peripheral Soft Reset==
All expansion peripherals should be reset when an output is performed to I/O port '''$F8FF'''.
Used by the standard BIOS functions
'''MC_BOOT_PROGRAM ''' and '''MC_START_PROGRAM ''' (vector BD13h vectors $BD13 and BD16h$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-pin connector to the board. The connections are labeled in the board as VCC (+5V), TR (Trigger), 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 witch interface interfaced directly with the Z80 CPU. You can get full information in the CTC datasheet ([[File:Z80ctc.pdf]]). The first thingto consider is how those channels are linked to the CTC-AY PlayCity board.
====Channel 0 ($F880)====
The channel 0 is exclusively used to generate the frequency of the two embedded soundchips (YMZ294). The input for the trigger
Used as a counter, it's synchronized with the CRTC CURSOR signal, generating a smooth high priority rasters interrupt. Used as a
timer (prescaler set to 256), it's its 15.625 kHz signal is scanline-synchronized. That means the time constant is the number of
scanlines to wait before to send an NMI.
====Channel 2/3 ($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/TO0TO2) is linked to the trigger for the channel 3 (TRG3). They can be used as 2x 8-bit or 1x 16-bitcounter/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 CTC-AY PlayCity board is populated with two AY compatible soundchips, adding 6 stereo channels. The YMZ294 eliminate the I/O port
and improve the CPU interface through /CS, /WR control signals and a 8-bit data bus. Each sound chip can be directly
programmed using two dedicated I/O ports for registers and data. No initialization code is required.
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-$0F90F) in the YMZ.The registers are write only.
===Coding Examples===
====YMZ Initialization====
{| class="wikitable"
|-
|-
| 1 || $$01 || 2,00 || 1,00 || = CPC
|-
| $2 || || 23,67 00 || 1,33 50 ||
|-
| $3 ||$02 || 3,00 33 || 1,50 67 ||
|-
| $4 || || 3,20 50 || 1,60 75 ||= ZX
|-
| $5 || $03 || 3,33 60 || 1,67 80 ||~ MSX
|-
| $6 || || 3,43 67 || 1,71 83 ||
|-
| $7 || $04 || 3,50 71 || 1,75 86 || ZX
|-
| $8 || || 3,56 75 || 1,78 88 || MSX
|-
| $9 || $05 || 3,60 78 || 1,80 89 ||
|-
| 10 || $A || 3,64 80 || 1,82 90 ||
|-
|-
| 12 || $C || 3,69 83 || 1,85 92 ||
|-
|-
| 14 || $E || 3,73 86 || 1,87 93 ||
|-
|-
| 16 || $0 || 3,76 98 || 1,88 99 ||~ ST
|-
|}
==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.
<pre>
; ---------------------------------------------------------------------------
; PlayCity check
; (c) 2013 SyX
; ---------------------------------------------------------------------------
; Constantes
CTC_TIM1 EQU $F881 ; Channel 1 (I: Cursor CRTC | O: NMI)
CTC_START_TIMER256 EQU %00110111
CTC_STOP_CHANNEL EQU %00000011
; ---------------------------------------------------------------------------
; NOTE: The lower ROM must be disabled before to run this code.
check_playcity
; Disable interrupts
DI
; Install NMI handler
LD A,$C3 ; JP $xxxx
LD HL,nmi_interrupt
LD ($0066),A
LD ($0067),HL
; Initialize playcity variable to 0
XOR A
LD (playcity),A
; Wait VBlank
LD B,$F5
.wait_vbl
IN A,(C)
RRA
JR NC,.wait_vbl
; Initialize CTC timer 1 (NMI generator)
LD HL,32 ; 32 scanlines
LD BC,CTC_TIM1
LD A,CTC_START_TIMER256
OUT (C),A ; Enable Timer
OUT (C),L ; Set new time constant
; Extra delay
LD IX,33 * 4 - 1 ; Wait 33 scanlines
CALL wait_scanlines_ix
LD A,(playcity)
OR A
JR NZ,.playcity_detected
; No PlayCity detected
.
.
.
.playcity_detected
.
.
.
; ---------------------------------------------------------------------------
nmi_interrupt
PUSH BC
PUSH AF
; Change playcity variable
LD A,$FF
LD (playcity),A
; Disable CTC timer 1 (NMI generator)
LD BC,CTC_TIM1
LD A,CTC_STOP_CHANNEL
OUT (C),A ; Disable Timer
POP AF
POP BC
EI
RETN
; ---------------------------------------------------------------------------
; Wait scanlines
; INPUT:
; IX: Scanlines to wait * 4 - 1
; ---------------------------------------------------------------------------
wait_scanlines_ix
DEFS 5,0 ; (5)
.loop_wait_scanlines_ix
DEFS 6 ; (6)
DEC IX ; (3)
LD A,IXH ; (2)
OR IXL ; (2)
JR NZ,.loop_wait_scanlines_ix ; (2/3)
; Total loop --> 16 * (IX - 1) + 15
RET ; (3)
; Total Routine --> 64 * SCANLINES
; ---------------------------------------------------------------------------
playcity
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.
== Links ==
*Website: [http://centpourcent.net centpourcent.net]
*[[Software Supporting PlayCity]]
*[https://framagit.org/offset/playcity-acepansion PlayCity ACEpansion] on Framagit
[[Category:FutureOS]]
[[Category:Music and sound]]
[[Category:Peripherals]]
