diff --git a/i2c-slave.c b/i2c-slave.c
index a91c74d..b66b4b7 100644
--- a/i2c-slave.c
+++ b/i2c-slave.c
@@ -27,13 +27,39 @@
 extern struct blmc_ blmc;
 extern struct ee_param params;
 
+/* SLA+R */
 #define CMD_WAIT		0x00
-#define CMD_GET_INFO		0x10
-#define CMD_SET_PWM		0x21
-#define CMD_GET_STATUS		0x22
-#define CMD_SET_PARAM		0x23
-#define CMD_GET_PARAM		0x24
-#define CMD_BOOT_LOADER		0x2F
+#define CMD_READ_VERSION	0x01
+#define CMD_READ_MEMORY		0x02
+/* internal mappings */
+#define CMD_READ_CHIPINFO	(0x10 | CMD_READ_MEMORY)
+#define CMD_READ_FLASH		(0x20 | CMD_READ_MEMORY)
+#define CMD_READ_EEPROM		(0x30 | CMD_READ_MEMORY)
+#define CMD_READ_PARAMETERS	(0x40 | CMD_READ_MEMORY)	/* only in APP */
+
+/* SLA+W */
+#define CMD_SWITCH_APPLICATION	CMD_READ_VERSION
+#define CMD_WRITE_MEMORY	CMD_READ_MEMORY
+/* internal mappings */
+#define CMD_BOOT_BOOTLOADER	(0x10 | CMD_SWITCH_APPLICATION)	/* only in APP */
+#define CMD_BOOT_APPLICATION	(0x20 | CMD_SWITCH_APPLICATION)
+#define CMD_WRITE_CHIPINFO	(0x10 | CMD_WRITE_MEMORY)	/* invalid */
+#define CMD_WRITE_FLASH		(0x20 | CMD_WRITE_MEMORY)
+#define CMD_WRITE_EEPROM	(0x30 | CMD_WRITE_MEMORY)
+#define CMD_WRITE_PARAMETERS	(0x40 | CMD_WRITE_MEMORY)	/* only in APP */
+
+/* CMD_SWITCH_APPLICATION parameter */
+#define BOOTTYPE_BOOTLOADER	0x00				/* only in APP */
+#define BOOTTYPE_APPLICATION	0x80
+
+/* CMD_{READ|WRITE}_* parameter */
+#define MEMTYPE_CHIPINFO	0x00
+#define MEMTYPE_FLASH		0x01
+#define MEMTYPE_EEPROM		0x02
+#define MEMTYPE_PARAMETERS	0x03				/* only in APP */
+
+
+
 
 const static uint8_t info[16] = "blmc m8-v1.2   ";
 
@@ -41,6 +67,8 @@ ISR(TWI_vect)
 {
 	static uint8_t cmd;
 	static uint8_t bcnt;
+	uint8_t data;
+	uint8_t ack = (1<<TWEA);
 
 	switch (TWSR & 0xF8) {
 	/* SLA + W received, ACK returned -> receive Data and ACK */
@@ -51,43 +79,78 @@ ISR(TWI_vect)
 
 	/* prev. SLA + W, data received, ACK returned -> receive Data and ACK */
 	case 0x80:
-		if (bcnt == 0) {
-			cmd = TWDR;
-			switch (cmd) {
-			case CMD_BOOT_LOADER:
-				wdt_enable(WDTO_15MS);
-
-			case CMD_GET_INFO:
-			case CMD_SET_PWM:
-			case CMD_GET_STATUS:
-			case CMD_SET_PARAM:
-			case CMD_GET_PARAM:
+		data = TWDR;
+		switch (bcnt) {
+		case 0:
+			switch (data) {
+			case CMD_SWITCH_APPLICATION:
+			case CMD_WRITE_MEMORY:
+				cmd = data;
 				bcnt++;
 				break;
 
 			default:
+				blmc.flags |= FLAG_I2C_ACTIVE;
+				setpwm(data);
 				cmd = CMD_WAIT;
 				bcnt = 0;
 				break;
 			}
+			break;
 
-		} else if (cmd == CMD_SET_PWM) {
-			blmc.flags |= FLAG_I2C_ACTIVE;
-			setpwm(TWDR);
-			bcnt = 0;
+		case 1:
+			switch (cmd) {
+			case CMD_SWITCH_APPLICATION:
+				if (data == BOOTTYPE_BOOTLOADER) {
+					wdt_enable(WDTO_15MS);
 
-		} else if (cmd == CMD_SET_PARAM) {
-			((uint8_t *)&params)[bcnt++ -1] = TWDR;
-			if (bcnt > sizeof(params)) {
-				write_parameters();
-				bcnt = 0;
+				} else {
+					ack = (0<<TWEA);
+				}
+				break;
+
+			case CMD_WRITE_MEMORY:
+				bcnt++;
+				if (data == MEMTYPE_PARAMETERS) {
+					cmd = CMD_WRITE_PARAMETERS;
+
+				} else {
+					ack = (0<<TWEA);
+				}
+				break;
+
+			default:
+				ack = (0<<TWEA);
+				break;
 			}
+			break;
 
-		} else {
-			bcnt = 0;
+		case 2:	/* ignore address bytes */
+		case 3:
+			bcnt++;
+			break;
+
+		default:
+			switch (cmd) {
+			case CMD_WRITE_PARAMETERS:
+				((uint8_t *)&params)[bcnt++ -4] = data;
+				if (bcnt == sizeof(params)) {
+					write_parameters();
+					ack = (0<<TWEA);
+				}
+				break;
+
+			default:
+				ack = (0<<TWEA);
+				break;
+			}
+			break;
 		}
 
-		TWCR |= (1<<TWINT) | (1<<TWEA);
+		if (ack == 0x00)
+			bcnt = 0;
+
+		TWCR |= (1<<TWINT) | ack;
 		break;
 
 	/* SLA+R received, ACK returned -> send data */
@@ -96,55 +159,27 @@ ISR(TWI_vect)
 	/* prev. SLA+R, data sent, ACK returned -> send data */
 	case 0xB8:
 		switch (cmd) {
-		case CMD_GET_INFO:
-			TWDR = info[bcnt++];
+		case CMD_WAIT:
+			data = 0x00;	/* TODO: transmit Current and MaxPWM */
+			break;
+
+		case CMD_READ_VERSION:
+			data = info[bcnt++];
 			bcnt %= sizeof(info);
 			break;
 
-		case CMD_GET_STATUS:
-			switch (bcnt++) {
-			case 0:	TWDR = blmc.pwm - blmc.pwm_limit;
-				break;
-
-			case 1:	TWDR = blmc.pwm;
-				break;
-
-			case 2:	TWDR = (blmc.rpm & 0xFF);
-				break;
-
-			case 3: TWDR = (blmc.rpm >> 8);
-				break;
-
-			case 4:	TWDR = (blmc.current & 0xFF);
-				break;
-
-			case 5: TWDR = (blmc.current >> 8);
-				break;
-
-			case 6:	TWDR = (blmc.voltage & 0xFF);
-				break;
-
-			case 7: TWDR = (blmc.voltage >> 8);
-				bcnt = 0;
-				break;
-
-			default:
-				bcnt = 0;
-				break;
-			}
-			break;
-
-		case CMD_GET_PARAM:
-			TWDR = ((uint8_t *)&params)[bcnt++];
+		case CMD_READ_PARAMETERS:
+			data = ((uint8_t *)&params)[bcnt++];
 			if (bcnt > sizeof(params))
 				bcnt = 0;
 			break;
 
 		default:
-			TWDR = 0xFF;
+			data = 0xFF;
 			break;
 		}
 
+		TWDR = data;
 		TWCR |= (1<<TWINT) | (1<<TWEA);
 		break;