--- nono/vm/scc.cpp	2026/04/29 17:04:56	1.1.1.7
+++ nono/vm/scc.cpp	2026/04/29 17:04:59	1.1.1.8
@@ -5,7 +5,9 @@
 //
 
 #include "scc.h"
+#include "bitops.h"
 #include "interrupt.h"
+#include "keyboard.h"
 #include "mpu.h"
 
 //          IODevice
@@ -51,9 +53,7 @@ SCCDevice::Read(uint32 offset)
 		return ReadCtrl(&cr.chan[1]);
 
 	 case 1:	// $E98003
-		// マウス非接続は 0x00 ?
-		putlog(0, "ChB データレジスタ読み込み (未実装)");
-		return 0x00;
+		return ReadData(&cr.chan[1]);
 
 	 case 2:	// $E98005
 		return ReadCtrl(&cr.chan[0]);
@@ -98,8 +98,7 @@ SCCDevice::Peek(uint32 offset)
 		return PeekCtrl(&cr.chan[1]);
 
 	 case 1:	// $E98003
-		// マウス非接続は 0x00 ?
-		return 0x00;
+		return PeekData(&cr.chan[1]);
 
 	 case 2:	// $E98005
 		return PeekCtrl(&cr.chan[0]);
@@ -247,6 +246,18 @@ SCCDevice::WriteCtrl(struct SIO::channel
 	}
 }
 
+void
+SCCDevice::WriteCR5(struct SIO::channel *chan, uint32 data)
+{
+	bool rts = bit_falling(chan->cr5, data, SIO::CR5_RTS);
+
+	inherited::WriteCR5(chan, data);
+
+	if (chan->id == 1 && rts) {
+		gKeyboard->MouseSendStart();
+	}
+}
+
 // 割り込みを上げる
 void
 SCCDevice::Interrupt()