izapple2/cardVidex.go

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package izapple2
import (
"errors"
"fmt"
"image"
"image/color"
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"time"
"github.com/ivanizag/izapple2/component"
)
/*
Videx 80 columns card for the Apple II+
See:
https://mirrors.apple2.org.za/Apple%20II%20Documentation%20Project/Interface%20Cards/80%20Column%20Cards/Videx%20Videoterm/Manuals/Videx%20Videoterm%20-%20Installation%20and%20Operation%20Manual.pdf
http://bitsavers.trailing-edge.com/components/motorola/_dataSheets/6845.pdf
https://glasstty.com/?p=660
*/
// CardVidex represents a Videx compatible 80 column card
type CardVidex struct {
cardBase
mc6845 component.MC6845
sramPage uint8
sram [0x800]uint8
upperROM memoryHandler
charGen []uint8
}
// NewCardVidex creates a new CardVidex
func NewCardVidex() *CardVidex {
var c CardVidex
c.name = "Videx 80 col Card"
// The C800 area has ROM and RAM
c.loadRomFromResource("<internal>/Videx Videoterm ROM 2.4.bin")
c.upperROM = c.romC8xx
c.romC8xx = &c
// The resource should be internal and never fail
c.loadCharacterMap("<internal>/80ColumnP110.BIN")
return &c
}
func (c *CardVidex) loadCharacterMap(filename string) error {
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bytes, _, err := LoadResource(filename)
if err != nil {
return err
}
size := len(bytes)
if size < 0x800 {
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return errors.New("character ROM size not supported for Videx")
}
c.charGen = bytes
return nil
}
func (c *CardVidex) assign(a *Apple2, slot int) {
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// TODO: use addCardSoftSwitches()
for i := uint8(0x0); i <= 0xf; i++ {
// Bit 0 goes to the RS pin of the MC6548. It controls
// whether a register is being accesed or the contents
// of the register is being accessed
rsPin := (i & 1) == 1
// Bits 2 and 3 determine which page will be selected
sramPage := i >> 2
ssName := fmt.Sprintf("VIDEXPAGE%v", sramPage)
if rsPin {
ssName += "REG"
} else {
ssName += "ADDRESS"
}
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c.addCardSoftSwitchR(i, func() uint8 {
c.sramPage = sramPage
return c.mc6845.Read(rsPin)
}, ssName+"R")
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c.addCardSoftSwitchW(i, func(value uint8) {
c.sramPage = sramPage
c.mc6845.Write(rsPin, value)
}, ssName+"W")
}
c.cardBase.assign(a, slot)
}
const videxRomLimit = uint16(0xcc00)
const videxSramLimit = uint16(0xce00)
const videxSramMask = uint16(0x01ff)
func (c *CardVidex) peek(address uint16) uint8 {
if address < videxRomLimit {
return c.upperROM.peek(address)
} else if address < videxSramLimit {
return c.sram[address&videxSramMask+uint16(c.sramPage)*0x200]
}
return 0
}
func (c *CardVidex) poke(address uint16, value uint8) {
if address >= videxRomLimit && address < videxSramLimit {
c.sram[address&videxSramMask+uint16(c.sramPage)*0x200] = value
}
}
func (c *CardVidex) setBase(base uint16) {
// Nothing
}
const (
videxCharWidth = uint8(8)
)
func (c *CardVidex) buildImage(light color.Color) *image.RGBA {
params := c.mc6845.ImageData()
width, height := params.DisplayedWidthHeight(videxCharWidth)
if (width == 0) || (height == 0) {
// No image available
size := image.Rect(0, 0, 3, 3)
img := image.NewRGBA(size)
img.Set(1, 1, color.White)
return img
}
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ms := time.Now().Nanosecond() / (1000 * 1000) // Host time, used for the cursoR blink
size := image.Rect(0, 0, width, height)
img := image.NewRGBA(size)
params.IterateScreen(func(address uint16, charLine uint8,
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cursorMode uint8, displayEnable bool,
column uint8, y int) {
bits := uint8(0)
if displayEnable {
char := c.sram[address&0x7ff]
bits = c.charGen[(uint16(char&0x7f)<<4)+uint16(charLine)]
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isCursor := false
switch cursorMode {
case component.MC6845CursorFixed:
isCursor = true
case component.MC6845CursorSlow:
// It should be 533ms (32/60, 32 screen refreshes)
// Let's make a 2 blinks per second
isCursor = ms/2 > 1000/4
case component.MC6845CursorFast:
// It should be 266ms (32/60, 16 screen refreshes)
// Let's make a 4 blinks per second
isCursor = ms/4 > 1000/8
}
if isCursor {
bits = ^bits
}
if char >= 128 {
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// Inverse
bits = ^bits
}
}
x := int(column) * int(videxCharWidth)
for i := 0; i < int(videxCharWidth); i++ {
pixel := (bits & 0x80) != 0
if pixel {
img.Set(x, y, light)
} else {
img.Set(x, y, color.Black)
}
bits <<= 1
x++
}
})
return img
}