106 lines
2.9 KiB
Go
106 lines
2.9 KiB
Go
|
package component
|
||
|
|
||
|
/*
|
||
|
MC6845 CRT Controller
|
||
|
See:
|
||
|
Motorola MC6845 datasheet
|
||
|
|
||
|
Pins:
|
||
|
RW, RS, D0-D7: Read() and Write()
|
||
|
MA0-13, RA04, CURSOR, DE: MC6845RasterCallBack()
|
||
|
*/
|
||
|
|
||
|
type MC6845 struct {
|
||
|
reg [18]uint8 // Internal registers R0 to R17
|
||
|
sel uint8 // Selected address register AR
|
||
|
}
|
||
|
|
||
|
func (m *MC6845) Read(rs bool) uint8 {
|
||
|
if !rs {
|
||
|
// AR is not readable
|
||
|
return 0x00
|
||
|
} else if m.sel >= 14 && m.sel <= 17 {
|
||
|
// Only R14 to R17 are readable
|
||
|
// Should we mask R14 and R16?
|
||
|
return m.reg[m.sel]
|
||
|
}
|
||
|
return 0x00
|
||
|
}
|
||
|
|
||
|
func (m *MC6845) Write(rs bool, value uint8) {
|
||
|
if !rs {
|
||
|
// AR is 5 bits
|
||
|
// What happens if AR > 17 ?
|
||
|
m.sel = value & 0x1f
|
||
|
} else if m.sel <= 15 {
|
||
|
// R0 to R15 are writable
|
||
|
m.reg[m.sel] = value
|
||
|
//fmt.Printf("Set %v to %v\n", m.sel, value)
|
||
|
}
|
||
|
}
|
||
|
|
||
|
func (m *MC6845) ImageData() MC6845ImageData {
|
||
|
var data MC6845ImageData
|
||
|
|
||
|
data.firstChar = uint16(m.reg[12]&0x3f)<<8 + uint16(m.reg[13])
|
||
|
data.charLines = (m.reg[9] + 1) & 0x1f
|
||
|
data.columns = m.reg[1]
|
||
|
data.lines = m.reg[6] & 0x7f
|
||
|
data.adjustLines = m.reg[5] & 0x1f
|
||
|
|
||
|
data.cursorPos = uint16(m.reg[14]&0x3f)<<8 + uint16(m.reg[15])
|
||
|
data.cursorStart = m.reg[10] & 0x1f
|
||
|
data.cursorEnd = m.reg[11] & 0x1f
|
||
|
// cursor mode is on bits 6 and 5 of R10
|
||
|
return data
|
||
|
}
|
||
|
|
||
|
type MC6845ImageData struct {
|
||
|
firstChar uint16 // 14 bits, address of the firt char on the first line
|
||
|
charLines uint8 // 5 bits, lines par character
|
||
|
columns uint8 // 8 bits, chars per line
|
||
|
lines uint8 // 7 bits, char lines per screen
|
||
|
adjustLines uint8 // 5 bits, extra blank lines
|
||
|
|
||
|
cursorPos uint16 // 14 bits, address? of the cursor position
|
||
|
cursorStart uint8 // 5 bits, cursor starting char row
|
||
|
cursorEnd uint8 // 5 bits, cursos ending char row
|
||
|
// cursor mode
|
||
|
|
||
|
}
|
||
|
|
||
|
func (data *MC6845ImageData) DisplayedWidthHeight(charWidth uint8) (int, int) {
|
||
|
return int(data.columns) * int(charWidth),
|
||
|
int(data.lines)*int(data.charLines) + int(data.adjustLines)
|
||
|
}
|
||
|
|
||
|
type MC6845RasterCallBack func(address uint16, charLine uint8, // Lookup in char ROM
|
||
|
cursor bool, displayEnable bool, // Modifiers
|
||
|
column uint8, y int) // Position in screen
|
||
|
|
||
|
func (data *MC6845ImageData) IterateScreen(callBack MC6845RasterCallBack) {
|
||
|
lineAddress := data.firstChar
|
||
|
y := 0
|
||
|
var address uint16
|
||
|
for line := uint8(0); line < data.lines; line++ {
|
||
|
for charLine := uint8(0); charLine < data.charLines; charLine++ {
|
||
|
address = lineAddress // Back to the first char of the line
|
||
|
for column := uint8(0); column < data.columns; column++ {
|
||
|
isCursor := (address == data.cursorPos) &&
|
||
|
(charLine >= data.cursorStart) &&
|
||
|
(charLine <= data.cursorEnd)
|
||
|
callBack(address, charLine, isCursor, true, column, y)
|
||
|
address = (address + 1) & 0x3fff // 14 bits
|
||
|
}
|
||
|
y++
|
||
|
}
|
||
|
lineAddress = address
|
||
|
}
|
||
|
for adjust := uint8(0); adjust <= data.adjustLines; adjust++ {
|
||
|
for column := uint8(0); column < data.columns; column++ {
|
||
|
callBack(0, 0, false, false, column, y) // lines with display not enabled
|
||
|
}
|
||
|
y++
|
||
|
}
|
||
|
}
|