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beeper: prescaler 32

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minjaesong
2026-06-20 21:10:28 +09:00
parent 646af9452c
commit 6c9a3fdc1e
4 changed files with 43 additions and 41 deletions
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43
tsvm_core/src/net/torvald/tsvm/peripheral/IOSpace.kt
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@@ -501,11 +501,11 @@ class IOSpace(val vm: VM) : PeriBase("io"), InputProcessor {
/**
* Built-in beeper / PSG speaker (terranmon.txt §93..99).
*
* A single square-wave tone generator modelled on the SN76489: a 14-bit frequency
* divider over a 3579545/16 Hz master clock, with optional 60 Hz arpeggio
* note-effects (two-, three- or four-note). The six command bytes (MMIO 94..99)
* are write staging; reading MMIO 93 latches them into the live tone ("upload
* beeper command").
* A single square-wave tone generator modelled on the SN76489: a 13-bit frequency
* divider over a 3579545/32 Hz master clock, with optional 60 Hz arpeggio
* note-effects (two-, three- or four-note) whose deltas are 11-bit. The six command
* bytes (MMIO 94..99) are write staging; reading MMIO 93 latches them into the live
* tone ("upload beeper command").
*
* The OpenAL device and its render thread are created lazily on the first non-silent
* upload, so a headless VM (no LibGDX OpenAL backend) simply stays silent.
@@ -514,11 +514,11 @@ private class Beeper {
companion object {
private const val SAMPLE_RATE = 48000
// SN76489 NTSC colourburst clock (3579545 Hz) after the chip's internal /16
// SN76489 NTSC colourburst clock (3579545 Hz) after the chip's internal /32
// prescaler. The square wave toggles every `divider` master ticks, so one full
// period spans 2*divider ticks -> f = MASTER_CLOCK / (2 * divider).
// (divider 254 -> 440.4 Hz, matching real SN76489 hardware.)
private const val MASTER_CLOCK = 3579545.4545454545 / 16.0
// (divider 127 -> 440.4 Hz.)
private const val MASTER_CLOCK = 3579545.4545454545 / 32.0
// Arpeggio note-effects step at 60 Hz: 48000 / 60 = 800 samples per step.
private const val SAMPLES_PER_ARP_TICK = SAMPLE_RATE / 60
private const val CHUNK = 512
@@ -526,16 +526,17 @@ private class Beeper {
}
// MMIO 94..99 write-staging registers:
// PPPPPPPP / pppppp_QQ / qqAABBCC / aaaaaaaa / bbbbbbbb / cccccccc
// where AA/BB/CC are the high two bits of the 10-bit arpeggio deltas A/B/C.
// PPPPPPPP / C_ppppp_QQ / AAABBBCC / aaaaaaaa / bbbbbbbb / cccccccc
// The 13-bit divider is PPPPPPPP:ppppp. AAA/BBB are the high three bits of the
// 11-bit deltas A/B; C's three high bits are split as C (byte 95 bit 7) : CC.
private val cmd = ByteArray(6)
// Latched ("uploaded") live command, read by the render thread.
@Volatile private var divider = 0 // 14-bit frequency divider; 0 = no sound
@Volatile private var divider = 0 // 13-bit frequency divider; 0 = no sound
@Volatile private var effect = 0 // QQ note-effect: 0 none, 1 four-note, 2 two-note, 3 three-note
@Volatile private var argA = 0 // A (10-bit divisor delta)
@Volatile private var argB = 0 // B (10-bit divisor delta)
@Volatile private var argC = 0 // C (10-bit divisor delta)
@Volatile private var argA = 0 // A (11-bit divisor delta)
@Volatile private var argB = 0 // B (11-bit divisor delta)
@Volatile private var argC = 0 // C (11-bit divisor delta)
@Volatile private var running = false
private var renderThread: Thread? = null
@@ -550,13 +551,13 @@ private class Beeper {
*/
fun upload(): Byte {
val hi = cmd[0].toInt() and 255 // PPPPPPPP
val lo = cmd[1].toInt() and 255 // pppppp_QQ
val ext = cmd[2].toInt() and 255 // qqAABBCC: high two bits of A/B/C
divider = (hi shl 6) or (lo ushr 2) // 14-bit frequency divider
effect = lo and 0b11 // QQ
argA = (((ext ushr 4) and 0b11) shl 8) or (cmd[3].toInt() and 255) // 10-bit A
argB = (((ext ushr 2) and 0b11) shl 8) or (cmd[4].toInt() and 255) // 10-bit B
argC = (((ext ) and 0b11) shl 8) or (cmd[5].toInt() and 255) // 10-bit C
val lo = cmd[1].toInt() and 255 // C_ppppp_QQ
val ext = cmd[2].toInt() and 255 // AAABBBCC: high three bits of A/B and the CC of C
divider = (hi shl 5) or ((lo ushr 2) and 0b11111) // 13-bit frequency divider
effect = lo and 0b11 // QQ
argA = (((ext ushr 5) and 0b111) shl 8) or (cmd[3].toInt() and 255) // 11-bit A
argB = (((ext ushr 2) and 0b111) shl 8) or (cmd[4].toInt() and 255) // 11-bit B
argC = (((lo ushr 7) and 0b1) shl 10) or ((ext and 0b11) shl 8) or (cmd[5].toInt() and 255) // 11-bit C
if (divider != 0) ensureStarted()
return (if (divider != 0) 1 else 0).toByte()
}