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--- x68000:screen_control [2014/06/29 22:45] – eidis
+++ x68000:screen_control [2019/08/27 20:45] (current) – external edit 127.0.0.1
@@ Line 10: / Line 10: @@
  X68000 has a very strong screen control mechanism that isn't seen in other personal computers. Almost screen view required in business-use computers are characters, and very easy graph view, so their hardwares have screens for characters (including kanji) and graphics in about 16 colors.
-On the other hand, X68000 is designed for deeling with several requirement about "views",such as real time action games,high definition with tens of thousands colors for example ray tracings,
+On the other hand, X68000 is designed for dealing with several requirement about "views",such as real time action games,high definition with tens of thousands colors for example ray tracings,
 window system with several character fonts, without overload of CPU.
  Figure 1(p.162) shows screen construction of X68000.
- X68000 has indivisual 4 types of screens:Graphic screen(1 to 4),text screen(4),sprite (128 max ,32 max on same horizontal lines),BackGround screens (up to 2). And X68000 composes them and video screen (super impose),then show in CRT.
+ X68000 has individual 4 types of screens:Graphic screen(1 to 4),text screen(4),sprite (128 max ,32 max on same horizontal lines),BackGround screens (up to 2). And X68000 composes them and video screen (super impose),then show in CRT.
 [p.162]
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 By The name "Text screen" we think it can only shows characters,
 but text screen of X68000 is a kind of graphics screens.It is useful that
-we can put dots on free position or elase them.
+we can put dots on free position or erase them.
 The Difference of the text screen and graphic screen is that ,in text screen ,bit arrays are in horizontal direction.That is 1 word data correspond to horizontal 16 dots.
-In graphic screen we must write 16 times to draw 16 dots even in monochrome mode,but in text screen we can write 1 time.So it is useful to show previouly prepareted patterns such as character patterns .
+In graphic screen we must write 16 times to draw 16 dots even in monochrome mode,but in text screen we can write 1 time.So it is useful to show previously prepared patterns such as character patterns .
 X68000 has 4 such text planes, and each plane corresponds to each bit of color code. Then max 16 colors selected from 65536 colors it can show.
@@ Line 61: / Line 61: @@
 We can use text or graphic screens for such purpose,but in case of game, BG screen is made for more efficient screen control paying attention to using many alike patterns.
 BG screen consists of 64x64 squares ,and 32x32 regions shown on display.
-Each square has corrensponding memory area and when we write pattern number
+Each square has corresponding memory area and when we write pattern number
 (0-255),registered pattern is shown.
-We can show each pattern indivisually in wanted area, but BG can show at the same time 32x32=1024 pattern(but we can use 192 pattern).
+We can show each pattern individually in wanted area, but BG can show at the same time 32x32=1024 pattern(but we can use 192 pattern).
-X68000 has 2 BG screen and we can select where we want to show by 1 unit dot about each 2 screen indivisually.So we can scroll smoothly backgrounds.
+X68000 has 2 BG screen and we can select where we want to show by 1 unit dot about each 2 screen individually.So we can scroll smoothly backgrounds.
 ====== 1-4 Sprite screen ======
@@ Line 71: / Line 71: @@
 X68000 can define 256 patterns (16dot x 16dot)and show max 128s.
 (but 32s on a horizontal line).Graphic screen or Text screen point to
-relative motion-less screen ,and sprite screen is confortable for the purpose
+relative motion-less screen ,and sprite screen is comfortable for the purpose
-such as action games which moves quickly patternd characters.
+such as action games which moves quickly patterned characters.
 If we try to such games on graphic screen or text screen,we must read the pattern data which a character moves to, and then we draw back the data after
 moving a character other position.
 By using sprite,such overlap is processed by hardware,so software only have to
 write designation resister of sprite position,then CPU load is very decreased.
-"GRADIUS" attached to Original X68000 is good example of fully pratical used
+"GRADIUS" attached to Original X68000 is good example of fully practical used
 of this Sprite function.
+[p.166]
+====== 2. Construction of each screens and Address allocation ======
+Display circuit of X68000 is very complicated which is operating simultaneously each having different type such as graphics, text, BG, and sprite screen and dealing with superimposing ,screen capture, and so on.
+So it may be difficult to understand when listing all resistors,then at first I will explain constructions of each screen that X68000 has ,and address allocation of visual  memory. In next section, functions of screen on/off,priority control.
+====== 2-1 Construction of graphic screen ======
+====== 2-1-1 Screen mode of graphic screen ======
+It is shown on Table 1, p.167 that list of screen mode which is considered X68000 supports.
+X68000 has many screen modes ,but when pay attention to number of dots,it is combination of 2 types of real screen and 4 types of display screen.
+In table, a double circle means that screen mode is supported by BASIC ,XC library, IOCS call.
+And a single circle means that screen mode is not supported by system software ,but is to exist in XC programmers manual and so on.
+And it is called high definition mode or normal definition mode in Table 1.
+That means simply horizontal scan frequency is 31kHz or 15kHz.
+It it strange 15kHz is called normal mode because X68000 usually uses 31kHz.
+But this term is often used in manuals by SHARP,so I follow a rule.
+kHz is used in analog TV(in Japan,but analog TV broadcast in Japan is discontinued),then if superimpose mode is used, we use 15kHz mode.
+In 15kHz we can use only screen mode whose dot number is 512 or 256.