Changes
correction of an error relating to IC
[[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 Array (VGA, not to be confused with the IBM PC compatible graphic card spec).
== Interrupt generation ==
[https://www.grimware.org/doku.php/documentations/devices/gatearraydo=export_xhtml#interrupt.generator Source: Grimware portal (Grim)]
On all CRTCsevery falling edge of the HSync signal, R52 interrupts always start 1µs after the end of an HSYNCGate Array will increment the counter by one. But on CRTCs 3/4When the counter reaches 52, HSYNCs occur 1µs later than on CRTCs 0/1/2. Which means that on CRTCs 3/4, interrupts start 1µs later than on CRTCs 0/1/2. This can be adjusted by using the Gate Array raise the INT signal and reset the counter. With 50Hz PAL CRTC register 3settings (one HSync every 64us) this will produce a 300Hz interrupt rate.
When the Gate Array sends an interrupt request:*If the interrupts were authorized at the time of the requesta VSync occurs, 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 will wait for two HSync and the interrupt takes place. This happens only '''after the instruction that follows EI''' as this Z80 instruction has a 1-instruction delay.:
The HSYNC and VSYNC signals are received from falling edge of the HSync trigger the counter, therefore modifying the duration of the HSync with the [[CRTC]]. These signals are then modified Register 3 can delay the interrupt requests by the Gate Array to C-HSYNC and C-VSYNC and merged into a single CSYNC signal that will few microseconds. This can be sent used to the display.adjust interrupt timings between CPC and Plus machines…
== Controlling the Gate Array ==
<br>
=== Palette sorted by Hardware Firmware Colour Numbers === The firmware colour palette is sorted by luminance value.
{| class="wikitable"
|-
!Firmware Number
!Hardware Number
!Colour Name
!R %
!G %
!ASIC
!Colour
|-
| 0 (40h) || 13 54h || 50Black || 50 0|| 50 0|| 0|| #666000|| bgcolor="#808080000000" | || White || Weiß || Gris
|-
| 1 (41h) || 44h (13or 50h) || 50Blue || 50 0|| 0|| 50|| #666006|| bgcolor="#808080000080" | || White || Weiß || Gris
|-
| 2 (42h) || 19 55h ||Bright Blue || 0||100 0|| 50100|| #0F600F|| bgcolor="#00ff800000ff" | || Sea Green || Seegrün || Verde mar
|-
| 3 (43h) || 25 5Ch ||100Red ||10050|| 50 0|| 0|| #FF6600|| bgcolor="#ffff80800000" | || Pastel Yellow || Pastellgelb || Amarillo pálido
|-
| 4 (44h) || 1 58h || 0Magenta || 50|| 0|| 50|| #006606|| bgcolor="#000080800080" | || Blue || Blau || Azul
|-
| 5 (45h) || 7 5Dh ||100Mauve || 50|| 0|| 50100|| #F0660F|| bgcolor="#ff00808000ff" | || Purple || Purpur || Púrpura
|-
| 6 (46h) || 10 4Ch ||Bright Red ||100|| 0|| 50|| 50 0|| #066F00|| bgcolor="#008080ff0000" | || Cyan || Blaugrün || Cyan
|-
| 7 || 45h (47hor 48h) || 16 Purple ||100|| 50 0|| 50|| #F66F06|| bgcolor="#ff8080ff0080" | || Pink || Rosa || Rosa
|-
| 8 (48h) || (7) 4Dh ||Bright Magenta ||100|| 0|| 50100|| #F06F0F|| bgcolor="#ff0080ff00ff" | || Purple || Purpur || Púrpura
|-
| 9 (49h) || (25) 56h ||100Green ||100 0|| 50|| 0|| #FF6060|| bgcolor="#ffff80008000" | || Pastel Yellow || Pastellgelb || Amarillo pálido
|-
| 10 (4Ah) || 24 46h ||100||100Cyan || 0|| 50|| 50|| #FF0066|| bgcolor="#ffff00008080" | || Bright Yellow || Hellgelb || Amarillo claro
|-
| 11 (4Bh) || 26 57h ||100Sky Blue ||100 0|| 50||100|| #FFF06F|| bgcolor="#ffffff0080ff" | || Bright White || Leuchtendweiß || Blanco
|-
| 12 (4Ch) || 6 5Eh ||100Yellow || 050|| 50|| 0|| #F00660|| bgcolor="#ff0000808000" | || Bright Red || Hellrot || Rojo claro
|-
| 13 || 40h (4Dhor 41h) || 8 White ||10050|| 050||10050|| #F0F666|| bgcolor="#ff00ff808080" | || Bright Magenta|| helles Magenta || Magenta claro
|-
| 14 (4Eh) || 15 5Fh ||100Pastel Blue || 50|| 050||100|| #F6066F|| bgcolor="#ff80008080ff" | || Orange || Orange || Anaranjado
|-
| 15 (4Fh) || 17 4Eh ||Orange ||100|| 50||100 0|| #F6FF60|| bgcolor="#ff80ffff8000" | || Pastel Magenta|| Pastell-magenta || Magenta pálido
|-
| 16 (50h) || (1) 47h || 0Pink || 0100|| 50|| 50|| #006F66|| bgcolor="#000080ff8080" | || Blue || Blau || Azul
|-
| 17 (51h) || (19) 4Fh || 0Pastel Magenta ||100|| 50||100|| #0F6F6F|| bgcolor="#00ff80ff80ff" | || Sea Green || Seegrün || Verde mar
|-
| 18 (|| 52h) || 18 Bright Green || 0||100|| 0|| #0F0|| bgcolor="#00ff00" | || Bright Green || Hellgrün || Verde claro
|-
| 19 || 42h (53hor 51h) || 20 Sea Green || 0||100||10050|| #0FF0F6|| bgcolor="#00ffff00ff80" | || Bright Cyan || helles Blaugrün || Cyan claro
|-
| 20 (54h) || 0 53h ||Bright Cyan || 0|| 0100|| 0100|| #0000FF|| bgcolor="#00000000ffff" | || Black || Schwarz || Negro
|-
| 21 (55h) || 2 5Ah || 0Lime || 050||100|| 0|| #00F6F0|| bgcolor="#0000ff80ff00" | || Bright Blue || Hellblau || Azul claro
|-
| 22 (56h) || 9 59h || 0Pastel Green || 50|| 0100|| 50|| #0606F6|| bgcolor="#00800080ff80" | || Green || Grün || Verde
|-
| 23 (57h) || 11 5Bh || 0Pastel Cyan || 50||100||100|| #06F6FF|| bgcolor="#0080ff80ffff" | || Sky Blue || Himmelblau || Azul cielo
|-
| 24 (58h) || 4 4Ah || 50Bright Yellow ||100||100|| 0|| 50|| #606FF0|| bgcolor="#800080ffff00" | || Magenta || Magenta || Magenta
|-
| 25 || 43h (59hor 49h) || 22 || 50||100|| 50|| #6F6|| bgcolor="#80ff80" | || Pastel Green Yellow || Pastellgrün 100|| Verde pálido|-| 26 (5Ah) || 21 100|| 50||100|| 0|| #6F0FF6|| bgcolor="#80ff00ffff80" | || Lime || Limonengrün || Lima
|-
| 27 (5Bh) 26|| 23 4Bh || 50Bright White ||100||100|| #6FF|| bgcolor="#80ffff" | || Pastel Cyan || Pastell-blaugrün|| Cyan pálido|-| 28 (5Ch) || 3 || 50|| 0|| 0|| #600|| bgcolor="#800000" | || Red || Rot || Rojo|-| 29 (5Dh) || 5 || 50|| 0||100|| #60FFFF|| bgcolor="#8000ffffffff" | || Mauve || Hellviolett || Violeta|-| 30 (5Eh) || 12 || 50|| 50|| 0|| #660|| bgcolor="#808000" | || Yellow || Gelb || Amarillo|-| 31 (5Fh) || 14 || 50|| 50||100|| #66F|| bgcolor="#8080ff" | || Pastel Blue || Pastellblau || Azul pálido
|}
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>
=== Intensities Amstrad Colour Names ===
<br>
=== Palette sorted by Firmware Hardware Colour Numbers === The firmware colour palette is sorted by luminance value.
{| class="wikitable"
|-
!Firmware Number
!R %
!G %
!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|-| 30 (5Eh) || 12 || 50|| 50|| 0|| #660|| bgcolor="#808000" | || Yellow || Gelb || Jaune || Amarillo
|-
|2631 (5Fh) || 4Bh ||Bright White 14 ||10050||10050||100|| #FFF66F||bgcolor="#ffffff8080ff"||| Pastel Blue || Pastellblau || Bleu pastel || Azul pastel
|}
<br>
=== Green Screen Colours Intensities ===
This explains why the Amstrad preferred engineers used the following values to propose a completely different image system, not comparable to a conversion to monochrome, which would have limited adapt the number of brightness levels old colour palette to 21 (for example, colours 9 and 6 would have had the same luminance).new 12-bit palette on the Amstrad Plus:* 0% became #0* 50% became #6. They opted specifically chose #6 for a table the 50% value instead of 27 linear brightness steps. They assigned values of 1 (1kΩ) for bluethe expected #7 or #8, 3 (3.3kΩ) for red, and 9 (10kΩ) for greento better match the real Amstrad CPC palette.* 100% became #F
<br>
=== To calculate the luminance value Green Screen Colours ===
'''GreenRed'''
*0% => do not add anything *50% => add 3 *100% => add 6
*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)]