--- nono/vm/sysport.cpp	2026/04/29 17:04:28	1.1.1.1
+++ nono/vm/sysport.cpp	2026/04/29 17:04:32	1.1.1.2
@@ -18,17 +18,29 @@ SysportDevice::~SysportDevice()
 {
 }
 
+// アドレスデコーダ
+inline uint64
+SysportDevice::Decoder(uint32 addr) const
+{
+	// 折り返しは?
+	addr -= baseaddr;
+
+	// 偶数アドレスはバスエラー?
+	if ((addr & 1) == 0)
+		return (uint64)-1;
+
+	return addr >> 1;
+}
+
 uint64
 SysportDevice::Read8(uint32 addr)
 {
 	uint32 data;
 
-	if ((addr % 2) == 0) {
-		return 0xff;
-	}
+	switch (Decoder(addr)) {
+	 default:
+		return (uint64)-1;
 
-	int n = (addr - baseaddr) / 2;
-	switch (n) {
 	 case SYSPORT::CONTRAST:
 		data = 0xf0 | sysport.contrast;
 		break;
@@ -39,8 +51,8 @@ SysportDevice::Read8(uint32 addr)
 		data = 0xff;
 		break;
 	 case SYSPORT::KEY:
-		// キーボードは接続されていない
-		data = 0x00;
+		// キーボードは接続されてることにする
+		data = 0x08;
 		break;
 	 case SYSPORT::WAIT:
 		data = 0xff;
@@ -51,8 +63,6 @@ SysportDevice::Read8(uint32 addr)
 	 case SYSPORT::SRAMWP:
 		data = 0xff;
 		break;
-	 default:
-		return (uint64)-1;
 	}
 	putlog(1, "$%06X -> $%02x", addr, data);
 	return data;
@@ -67,12 +77,10 @@ SysportDevice::Read16(uint32 addr)
 uint64
 SysportDevice::Write8(uint32 addr, uint32 data)
 {
-	if ((addr % 2) == 0) {
+	switch (Decoder(addr)) {
+	 default:
 		return (uint64)-1;
-	}
 
-	int n = (addr - baseaddr) / 2;
-	switch (n) {
 	 case SYSPORT::CONTRAST:
 		sysport.contrast = data & 15;
 		break;
@@ -105,9 +113,6 @@ SysportDevice::Write8(uint32 addr, uint3
 	 case SYSPORT::POWEROFF:
 		putlog(0, "$E8E00F (POWEROFF) 未サポート書き込み %02x", data);
 		break;
-
-	 default:
-		return (uint64)-1;
 	}
 	return 0;
 }
@@ -123,12 +128,7 @@ SysportDevice::Peek8(uint32 addr)
 {
 	uint32 data;
 
-	if ((addr % 2) == 0) {
-		return 0xff;
-	}
-
-	int n = (addr - baseaddr) / 2;
-	switch (n) {
+	switch (Decoder(addr)) {
 	 case SYSPORT::CONTRAST:
 		data = 0xf0 | sysport.contrast;
 		break;