[[File:Amstrad 40007 Gate Array .png|right|thumb|Amstrad 40007 Gate Array]][[File:Amstrad 40010 Gate Array.png|right|thumb|Amstrad 40010 Gate Array]]
Also designated as Video gate Gate Array (VGA, not to be confused with the IBM PC compatible graphic card spec).
<br>
In the [[KC Compact]] system, the functions of the Gate Array are "emulated" in TTL chips, [[CIO Overview|CIO]], and its color translation EPROM.
In the "cost-down" version of the CPC6128, the functions of the Gate Array are integrated into a an ASIC.
<br>
*If the interrupts were authorized at the time of the request, then bit5 of R52 is cleared (but R52 was reset to 0 anyway) and the interrupt takes place
*If interrupts are not authorized, then the R52 counter continues to increment and the interrupt remains armed (the Gate Array then maintains its INT signal). When interrupts are enabled (using the EI instruction), bit5 of R52 is cleared and the interrupt takes place. This happens only '''after the instruction that follows EI''' as this Z80 instruction has a 1-instruction delay.
[https://shaker.logonsystem.eu/ACCC1.8-EN.pdf Source]
Note: On Amstrad Plus, the interrupt management system is seriously beefed up. See the [[ASIC]] wiki page.
On a CPC monitor, the CSYNC is rendered in "absolute black". It is darker than the palette colour black output by the Gate Array. The electron beam is basically turned off. Turning up the brightness level won't make it any brighter.
[https://shaker.logonsystem.eu/ACCC1.8-EN.pdf Source]
<br>
The recommended I/O port address is &7Fxx.
The Gate Array is not connected to the CPU's RD and WR pins, so it cannot detect the bus's I/O direction. If you execute an I/O read operation on the Gate Array I/O address, the Gate Array will read an unpredictable value from the databus which will be in high-impedance state. If the value is a valid Gate Array command, it will be executed, otherwise nothing will happen. [https://www.grimware.org/doku.php/documentations/devices/gatearraydo=export_xhtml Source]
The function to be performed is selected by writing data to the Gate Array, the first bits of the data define the function selected (see table below). It is not possible to read from the Gate Array.
| 1 || 0 || 0 || style="text-align: center;" | n || All || RMR || Control Interrupt counter, ROM mapping and Graphics mode || Gate Array
|-
| rowspan="2"| 1 || rowspan="2"| 0 || rowspan="2"| 1 || style="text-align: center;" rowspan="2" | n || All || RMR || ''Ghost register'' || Gate Array (CPC) or locked ASIC (Plus)
|-
| 1 || 0 || 1 || style="text-align: center;" | n || Plus || RMR2 || ASIC & Advanced ROM mapping || Unlocked ASIC
|-
| 1 || 1 ||colspan=2 style="text-align: center;" | n || All || MMR || RAM memory mapping || PAL (only with 128KB or RAM expansion)
In the CPC464, CPC664 and KC compact, MMR is performed in an external memory expansion (e.g. Dk'Tronics 64K RAM Expansion), if this expansion is not present then MMR is not available.
In the CPC6128, MMR is performed by a [[PAL16L8|PALchip]] located on the main PCB, or an external memory expansion.
In the 464+ and 6128+, MMR is performed by the ASIC or an external memory expansion. Please read the document on RAM management for more information.
==== ROM configuration selection ====
Bit 2 is used to enable or disable the lower ROM area. The lower ROM area occupies memory addresses &0000-&3fff and is used to access the operating system ROM. When the lower ROM area is is enabled, reading from &0000-&3FFF will return data in the ROM. When a value is written to &0000-&3FFF, it will be written to the RAM underneath the RAMROM. When it is disabled, data read from &0000-&3FFF will return the data in the RAM.
Similarly, bit 3 controls enabling or disabling of the upper ROM area. The upper ROM area occupies memory addressess &C000-&FFFF and is BASIC or any expansion ROMs which may be plugged into a ROM board/box. See the document on [[Upper ROM Bank Number|upper rom selection]] for more details. When the upper ROM area enabled, reading from &c000-&ffff, will return data in the ROM. When data is written to &c000-&FFFF, it will be written to the RAM at the same address as the ROM. When the upper ROM area is disabled, and data is read from &c000-&ffff it will be the data in the RAM.
Bit 4 controls the interrupt generation. It can be used to delay interrupts. See the document on interrupt generation for more information.
==== Summary ====
| 5 || 1
|-
| 4 || x || rowspan="2" |Lower ROM address and ASIC I/O page RMR addressing mode
|-
| 3 || x
|}
The lower {| class="wikitable"|+ RMR addressing modes!Bit 4!Bit 3!Lower ROM address and ![[Default I/O Port SummaryASIC|ASIC I/O page]] modes are: |-Mode- ROM address ASIC I/O Page 00 |0|0|&0000-&3FFF |Disabled 01 |-|0|1|&4000-&7FFF |Disabled 10 |-|1|0|&8000-&BFFF |Disabled 11 |-|1|1|&0000-&3FFF |&4000-&7fff7FFF|}
The physical ROMs are also accessible as upper ROMs by using the [[Upper ROM Bank Number]] port and the RMR register.
=== Register MMR (RAM memory mapping) ===
This register exists only in CPCs with 128K RAM (like the CPC 6128), or CPCs equipped with [[Standard Memory Expansions]]). Note: In the CPC 6128, the register is a separate [[PAL16L8|PAL chip]] that assists the Gate Array chip. See its wiki page.
{| class="wikitable"
!colspan=8|Displayed Pixels
!rowspan=2|Definition
!rowspan=2|Pixel clock
!rowspan=2|Default resolution
|-
!7
|colspan=4 style="text-align: center;"|A
|colspan=4 style="text-align: center;"|B
|2 pixels in 16 colorscolours|4 MHz|160x200, 20-column text
|-
|1
|colspan=2 style="text-align: center;"|D
|4 pixels in 4 colours
|8 MHz
|320x200, 40-column text
|-
|2
|G
|H
|8 pixels in 2 colorscolours|16 MHz|640x200, 80-column text
|-
|3
|colspan=4 style="text-align: center;"|A
|colspan=4 style="text-align: center;"|B
|2 pixels in 4 colorscolours|4 MHz|160x200, 20-column text
|}
<br>
=== Palette sorted by Hardware Firmware Colour Numbers ===
The firmware colour palette is sorted by luminance value. {| class="FCK__ShowTableBorderswikitable"
|-
| ''Hardware Number||Firmware Number|| ''Colour Name''
| ''R %'' || ''G %'' || ''B %'' || ''ASIC'' || ''Colour''
|-
| 0 (40h) || 13 || White || 50|| 50|| 50|| #666|| bgcolor="#808080" | !Firmware Number!Hardware Number!Colour Name!R %!G %!B %!ASIC!Colour
|-
| 1 (41h) 0|| (13) 54h || White Black || 50 0|| 50 0|| 50 0|| #666000|| bgcolor="#808080000000" |
|-
| 2 1|| 44h (42hor 50h) || 19 || Sea Green Blue || 0||100 0|| 50|| #0F6006|| bgcolor="#00ff80000080" |
|-
| 3 (43h) 2|| 25 55h || Pastel Yellow Bright Blue ||100 0||100 0|| 50100|| #FF600F|| bgcolor="#ffff800000ff" |
|-
| 4 (44h) 3|| 1 5Ch || Blue Red || 50|| 0|| 0|| 50|| #006600|| bgcolor="#000080800000" |
|-
| 5 (45h) 4|| 7 58h || Purple Magenta ||10050|| 0|| 50|| #F06606|| bgcolor="#ff0080800080" |
|-
| 6 (46h) 5|| 10 5Dh || Cyan Mauve || 50|| 0|| 50|| 50100|| #06660F|| bgcolor="#0080808000ff" |
|-
| 7 (47h) 6|| 16 4Ch || Pink Bright Red ||100|| 50 0|| 50 0|| #F66F00|| bgcolor="#ff8080ff0000" |
|-
| 8 (48h) 7|| 45h (7or 48h) || Purple ||100|| 0|| 50|| #F06|| bgcolor="#ff0080" |
|-
| 9 (49h) 8|| (25) 4Dh || Pastel Yellow Bright Magenta ||100||100 0|| 50100|| #FF6F0F|| bgcolor="#ffff80ff00ff" |
|-
| 10 (4Ah) 9|| 24 56h || Bright Yellow Green ||100 0||10050|| 0|| #FF0060|| bgcolor="#ffff00008000" |
|-
| 11 (4Bh) 10|| 26 46h || Bright White Cyan ||100 0||10050||10050|| #FFF066|| bgcolor="#ffffff008080" |
|-
| 12 (4Ch) 11|| 6 57h || Bright Red ||100Sky Blue || 0|| 050||100|| #F0006F|| bgcolor="#ff00000080ff" |
|-
| 13 (4Dh) 12|| 8 5Eh || Bright MagentaYellow ||10050|| 050||100 0|| #F0F660|| bgcolor="#ff00ff808000" |
|-
| 14 13|| 40h (4Ehor 41h) || 15 White || Orange ||10050|| 50|| 050|| #F60666|| bgcolor="#ff8000808080" |
|-
| 15 (4Fh) 14|| 17 5Fh || Pastel MagentaBlue ||10050|| 50||100|| #F6F66F|| bgcolor="#ff80ff8080ff" |
|-
| 16 (50h) 15|| (1) 4Eh || Blue Orange || 0100|| 50|| 0|| 50|| #006F60|| bgcolor="#000080ff8000" |
|-
| 17 (51h) 16|| (19) 47h || Sea Green Pink || 0100||10050|| 50|| #0F6F66|| bgcolor="#00ff80ff8080" |
|-
| 18 (52h) 17|| 18 4Fh || Bright Green Pastel Magenta || 0100||10050|| 0100|| #0F0F6F|| bgcolor="#00ff00ff80ff" |
|-
| 19 (53h) 18|| 20 52h || Bright Cyan Green || 0||100||100 0|| #0FF0F0|| bgcolor="#00ffff00ff00" |
|-
| 20 19|| 42h (54hor 51h) || 0 || Black Sea Green || 0|| 0100|| 050|| #0000F6|| bgcolor="#00000000ff80" |
|-
| 21 (55h) 20|| 2 53h || Bright Blue Cyan || 0|| 0100||100|| #00F0FF|| bgcolor="#0000ff00ffff" |
|-
| 22 (56h) 21|| 9 5Ah || Green Lime || 050|| 50100|| 0|| #0606F0|| bgcolor="#00800080ff00" |
|-
| 23 (57h) 22|| 11 59h || Sky Blue || 0Pastel Green || 50||100|| 50|| #06F6F6|| bgcolor="#0080ff80ff80" |
|-
| 24 (58h) 23|| 4 5Bh || Magenta Pastel Cyan || 50|| 0100|| 50100|| #6066FF|| bgcolor="#80008080ffff" |
|-
| 25 (59h) 24|| 22 4Ah || Pastel Green Bright Yellow || 50100||100|| 50 0|| #6F6FF0|| bgcolor="#80ff80ffff00" |
|-
| 26 (5Ah) || 21 || Lime || 50||100|| 0|| #6F0|| bgcolor="#80ff00" | 25|-| 27 43h (5Bhor 49h) || 23 || Pastel Cyan Yellow || 50100||100||10050|| #6FFFF6|| bgcolor="#80ffffffff80" |
|-
| 28 (5Ch) 26|| 3 4Bh || Red Bright White || 50|| 0|| 0|| #600||bgcolor="#800000" | |-| 29 (5Dh) || 5 || Mauve || 50|| 0100||100|| #60F||bgcolor="#8000ff" | |-| 30 (5Eh) || 12 || Yellow || 50|| 50|| 0|| #660||bgcolor="#808000" | |-| 31 (5Fh) || 14 || Pastel Blue || 50|| 50||100|| #66FFFF||bgcolor="#8080ffffffff" |
|}
Note: We can observe that the official Amstrad names of some colours are a bit silly: "red" is in fact brown, "yellow" is in fact khaki and "white" is in fact grey.
<br>
=== Palette sorted by Firmware Amstrad Colour Numbers Names ===
<gallery>Cpc 6128 master colour chat.jpg|Master colour chartCpc 6128 farbtabelle.jpg|FarbtabelleCpc 6128 palette des couleurs.jpg|Palette des couleursCpc 6128 tabla de colores.jpg|Tabla de colores</gallery> <br> === Palette sorted by Hardware Colour Numbers === {| class="FCK__ShowTableBorderswikitable"
|-
| ''Firmware Number'' || ''!Hardware Number'' || ''Colour Name'' | ''!Firmware Number!R %'' || ''!G %'' || ''!B %'' || ''!ASIC'' || ''!Colour''!Colour Name!German Name!French Name!Spanish Name
|-
| 0(40h) || 54h 13 ||Black 50|| 050|| 0|| 050|| #000666||bgcolor="#000000808080"||| White || Weiß || Blanc || Blanco
|-
| 1(41h) || 44h (or 50h13) ||Blue 50|| 0|| 050|| 50|| #006666||bgcolor="#000080808080"||| White || Weiß || Blanc || Blanco
|-
| 2(42h) || 55h ||Bright Blue 19 || 0|| 0100||10050|| #00F0F6||bgcolor="#0000ff00ff80"||| Sea Green || Seegrün || Vert marin || Verde marino
|-
| 3(43h) || 5Ch 25 ||Red 100|| 50100|| 0|| 050|| #600FF6||bgcolor="#800000ffff80"||| Pastel Yellow || Pastellgelb || Jaune pastel || Amarillo pastel
|-
| 4(44h) || 58h 1 ||Magenta || 50 0|| 0|| 50|| #606006||bgcolor="#800080000080"||| Blue || Blau || Bleu || Azul
|-
| 5(45h) || 5Dh 7 ||Mauve || 50100|| 0||10050|| #60FF06||bgcolor="#8000ffff0080"||| Purple || Purpur || Pourpre || Púrpura
|-
| 6(46h) || 4Ch ||Bright Red ||10010 || 0|| 050|| 50|| #F00066||bgcolor="#ff0000008080"||| Cyan || Blaugrün || Turquoise || Ciano
|-
| 7|| 45h (or 48h47h) ||Purple 16 ||100|| 050|| 50|| #F06F66||bgcolor="#ff0080ff8080"||| Pink || Rosa || Rose || Rosa
|-
| 8(48h) || 4Dh ||Bright Magenta (7) ||100|| 0||10050|| #F0FF06||bgcolor="#ff00ffff0080"||| Purple || Purpur || Pourpre || Púrpura
|-
| 9(49h) || 56h (25) ||Green 100|| 0100|| 50|| 0|| #060FF6||bgcolor="#008000ffff80"||| Pastel Yellow || Pastellgelb || Jaune pastel || Amarillo pastel
|-
|10(4Ah) || 46h 24 ||Cyan 100||100|| 0|| 50|| 50|| #066FF0||bgcolor="#008080ffff00"||| Bright Yellow || Hellgelb || Jaune vif || Amarillo brillante
|-
|11(4Bh) || 57h 26 ||Sky Blue 100|| 0|| 50100||100|| #06FFFF||bgcolor="#0080ffffffff"||| Bright White || Leuchtendweiß || Blanc brillant || Blanco brillante
|-
|12(4Ch) || 5Eh 6 ||Yellow 100|| 50|| 50 0|| 0|| #660F00||bgcolor="#808000ff0000"||| Bright Red || Hellrot || Rouge vif || Rojo brillante
|-
|13|| 40h (or 41h4Dh) ||White 8 || 50100|| 50 0|| 50100||#666F0F||bgcolor="#808080ff00ff"||| Bright Magenta|| helles Magenta || Magenta vif || Magenta brillante
|-
|14(4Eh) || 5Fh 15 ||Pastel Blue 100|| 50|| 50||100 0|| #66FF60||bgcolor="#8080ffff8000"||| Orange || Orange || Orange || Naranja
|-
|15(4Fh) || 4Eh ||Orange 17 ||100|| 50|| 0100|| #F60F6F|| bgcolor="#ff8000ff80ff"||| Pastel Magenta|| Pastell-magenta || Magenta pastel || Magenta pastel
|-
|16(50h) || 47h (1) ||Pink 0||100|| 50 0|| 50|| #F66006||bgcolor="#ff8080000080"||| Blue || Blau || Bleu || Azul
|-
|17(51h) || 4Fh (19) ||Pastel Magenta 0||100|| 50||100|| #F6F0F6||bgcolor="#ff80ff00ff80"||| Sea Green || Seegrün || Vert marin || Verde marino
|-
|18|| (52h ) ||Bright Green 18 || 0||100|| 0|| #0F0||bgcolor="#00ff00"||| Bright Green || Hellgrün || Vert vif || Verde brillante
|-
|19|| 42h (or 51h53h) ||Sea Green 20 || 0||100|| 50100|| #0F60FF||bgcolor="#00ff8000ffff"||| Bright Cyan || helles Blaugrün || Turquoise vif || Ciano brillante
|-
|20(54h) || 53h ||Bright Cyan 0 || 0||100 0||100 0|| #0FF000||bgcolor="#00ffff000000"||| Black || Schwarz || Noir || Negro
|-
|21(55h) || 5Ah 2 ||Lime 0|| 50 0||100|| 0|| #6F000F||bgcolor="#80ff000000ff"||| Bright Blue || Hellblau || Bleu vif || Azul brillante
|-
|22(56h) || 59h 9 ||Pastel Green 0|| 50||100|| 50 0|| #6F6060||bgcolor="#80ff80008000"||| Green || Grün || Vert || Verde
|-
|23(57h) || 5Bh 11 ||Pastel Cyan 0|| 50||100||100|| #6FF06F||bgcolor="#80ffff0080ff"||| Sky Blue || Himmelblau || Bleu ciel || Azul cielo
|-
|24(58h) || 4Ah 4 ||Bright Yellow ||100||10050|| 0|| 50|| #FF0606||bgcolor="#ffff00800080"||| Magenta || Magenta || Magenta || Magenta
|-
|25(59h) || 22 || 50||100|| 50|| #6F6|| bgcolor="#80ff80" | || Pastel Green || Pastellgrün || Vert pastel || Verde pastel|-| 43h 26 (or 49h5Ah) ||Pastel Yellow 21 || 50||100|| 0|| #6F0|| bgcolor="#80ff00" | || Lime || Limonengrün || Vert citron || Verde lima|-| 27 (5Bh) || 23 || 50||100||100|| #6FF|| bgcolor="#80ffff" | || Pastel Cyan || Pastell-blaugrün|| Turquoise pastel|| Ciano pastel|-| 28 (5Ch) || 3 || 50|| 0|| 0||#FF6600||bgcolor="#ffff80800000"||| Red || Rot || Rouge || Rojo|-| 29 (5Dh) || 5 || 50|| 0||100|| #60F|| bgcolor="#8000ff" | || Mauve || Hellviolett || Mauve || Malva
|-
|2630 (5Eh) || 4Bh 12 || 50|| 50|| 0|| #660|| bgcolor="#808000" | || Yellow || Gelb || Jaune || Amarillo|-| 31 (5Fh) ||Bright White 14 ||10050||10050||100|| #FFF66F||bgcolor="#ffffff8080ff"||| Pastel Blue || Pastellblau || Bleu pastel || Azul pastel
|}
Note: We can observe that the official Amstrad names of some colours are a bit silly. For example, "red" is in fact brown and "white" is in fact grey.
<br>
The 0%, 50%, and 100% values in the above tables are "should-be" values. However, the real hardware doesn't exactly match that intensities. The actual intensities depend on the luminance mixing (R,G,B tied together via resistors), on chipset (classic CPC, or newer ASIC ones), and on the load applied by external hardware (Monitor, or TV set).
On an actual Amstrad CPC, the half-intensity colour signal is measured to be closer to 40% rather than the expected 50%. This was verified by [[Grim ]] and independently confirmed by [[Nocash]]. [https://www.grimware.org/doku.php/documentations/devices/gatearray#inkr Source]
* [[CPC Palette]] - some more details
This explains why the Amstrad engineers used these the following values to adapt the old colour palette to the new 12-bit palette on the Amstrad Plus:
* 0% became #0
* 50% became #6. They specifically chose #6 for the 50% value instead of the expected #7 or #8, to better match the real Amstrad CPC palette.
* 100% became #F
They specifically chose #6 for the 50% value instead of #7, to better match the real Amstrad CPC palette.
<br>
=== Green Screen Colours ===
On a green screen (, where all colours are shades of unsaturated green), the firmware colours (in BASIC colours) are in order of increasing intensity. Black is very darkdarkest green, and bright white is bright brightest green, and firmware colour 13 is a medium green. (Thanks to [[Mark Rison|Mark Rison]] for this information)
The luminance (Y) is not exactly correlated to the actual luminance of colour images broadcast in RGB. We have other values. Amstrad preferred to propose a completely different image system, not comparable to a conversion to monochrome, which would have limited the number of brightness levels to 21 (for example, colours 9 and 6 would have had the same luminance).
They opted for a table of 27 linear brightness steps. They assigned values of 1 (1kΩ) for blue, 3 (3.3kΩ) for red, and 9 (10kΩ) for green.
<br> ==== To calculate the luminance value ====
'''Red'''
*0% => do not add anything *50% => add 3 *100% => add 6
'''Green'''
*0% => do not add anything *50% => add 9 *100% => add 18
'''Blue'''
*0% => do not add anything *50% => add 1 *100% => add 2
<br>
== External links ==
*[https://bread80.com/2021/06/03/understanding-the-amstrad-cpc-video-ram-and-gate-array-subsystem/ Electronic signals analysis of the Gate Array by Bread80]
* [https://shaker.logonsystem.eu/ACCC1.8-EN.pdf Gate Array documentation in Amstrad CRTC Compendium]
* [https://www.grimware.org/doku.php/documentations/devices/gatearray Gate Array documentation from Grimware]
* [http://quasar.cpcscene.net/doku.php?id=assem:gate_array Quasar Gate Array documentation (in french)]