diff --git a/main.c b/main.c
index 694cca0..4aae709 100644
--- a/main.c
+++ b/main.c
@@ -58,12 +58,16 @@ int main(void)
     uint16_t ramp = 0;
     uint8_t step = 0;
 
+    /* wait for complete update */
+    rgb_update(COLOR_MASK, 1);
+
     while (1) {
+        mpm_check_transfer();
+
+#if 0
         /* wait for complete update */
         rgb_update(COLOR_MASK, 1);
 
-#if 1
-
 //         _delay_ms(100);
 
         step++;
diff --git a/mpmctrl.c b/mpmctrl.c
index f6db845..bd801c1 100644
--- a/mpmctrl.c
+++ b/mpmctrl.c
@@ -21,44 +21,83 @@
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include <avr/wdt.h>
+#include <stdio.h>              /* NULL */
 
 #include "rgb16mpm.h"
 
+/* Dummy Wait:
+ * req: <cmd:0x00> <len[2]:0x0000>
+ * rsp: <cmd:0x00 <cause:0x00> <len[2]:0x0000>
+ */
 #define CMD_WAIT                0x00
+
+/* Switch Run Mode:
+ * req: <cmd:0x01> <len[2]:0x0001> <mode>
+ * rsp: <cmd:0x01> <cause> <len[2]:0x0000>
+ */
 #define CMD_SWITCH_MODE         0x01
+
+/* Get Software Version:
+ * req: <cmd:0x02> <len[2]:0x0000>
+ * rsp: <cmd:0x02> <cause> <len[2]> <version>
+ */
 #define CMD_GET_VERSION         0x02
-#define CMD_GET_CHIPINFO        0x03    /* bootloader / mpmboot */
-#define CMD_READ_MEMORY         0x11    /* bootloader / mpmboot */
-#define CMD_WRITE_MEMORY        0x12    /* bootloader / mpmboot */
-#define CMD_WRITE_COLOR         0x81
-#define CMD_WRITE_RAW_COLOR     0x82
-#define CMD_READ_RAW_COLOR      0x83
-#define CMD_WRITE_CONFIG        0x81
+
+/* Write RAW color:
+ * req: <cmd:0x80> <len[2]> <firstchannel> <RGB[x][3]>
+ * rsp: <cmd:0x80> <cause>,<len[2]:0x0000>
+ */
+#define CMD_WRITE_RAW_COLOR     0x80
+#define CMD_WRITE_INIT_COLOR    0x82
+
+/* Read RAW color:
+ * req: <cmd:0x80> <len[2]> <firstchannel> <count>
+ * rsp: <cmd:0x80> <cause>,<len[2]> <RGB[x][3]>
+ */
+#define CMD_READ_RAW_COLOR      0x81
+#define CMD_READ_INIT_COLOR     0x83
+
+/* response causes */
+#define CAUSE_SUCCESS           0x00
+#define CAUSE_NOT_SUPPORTED     0xF0
+#define CAUSE_INVALID_PARAMETER 0xF1
+#define CAUSE_UNSPECIFIED_ERROR 0xFF
+
+/* parameter for CMD_SWITCH_MODE */
+#define BOOTMODE_BOOTLOADER     0x00
+#define BOOTMODE_APPLICATION    0x80
 
 #define UART_CALC_BAUDRATE(baudRate) (((uint32_t)F_CPU) / (((uint32_t)baudRate)*16) -1)
 
-const static uint8_t versioninfo[16] = "rgb16mpm v0.99";
+static void mpm_reply(uint8_t cmd, uint8_t cause, uint16_t length, uint8_t *data);
 
-static uint8_t rx_cmd;
-static uint16_t rx_bcnt = 0xFF;
+const static uint8_t versioninfo[16] = VERSION_STRING;
+
+#define MPM_MAX_DATA_SIZE       64
+
+static uint8_t  mpm_data[MPM_MAX_DATA_SIZE];
+
+static uint8_t  rx_cmd;
+static uint16_t rx_bcnt;
 static uint16_t rx_length;
+static volatile uint8_t rx_ready;
 
-static uint8_t tx_cmd;
-static uint8_t tx_cause;
-static uint16_t tx_length;
+static uint8_t  tx_cmd;
+static uint8_t  tx_cause;
 static uint16_t tx_bcnt;
+static uint16_t tx_length;
+static uint8_t *tx_data;
+
 
 ISR(USART_RXC_vect)
 {
     uint8_t data = UDR;
     sei();
 
-    if (rx_bcnt == 0xFF) {
-        /* MPM address stored in TWI address register by bootloader */
-        if (data == TWAR) {
-            UCSRA &= ~(1<<MPCM);
-            rx_bcnt = 0;
-        }
+    /* MPM address stored in TWI address register by bootloader */
+    if ((UCSRA & (1<<MPCM)) && (data == TWAR)) {
+        UCSRA &= ~(1<<MPCM);
+        rx_bcnt = 0;
 
     } else {
         if (rx_bcnt == 0) {
@@ -67,29 +106,33 @@ ISR(USART_RXC_vect)
         } else if ((rx_bcnt == 1) || (rx_bcnt == 2)) {
             rx_length = (rx_length << 8) | data;
 
-        } else if ((rx_bcnt -3) < rx_length) {
-            // TODO: get data
+        } else if ((rx_bcnt -3) < MPM_MAX_DATA_SIZE) {
+            mpm_data[rx_bcnt -3] = data;
         }
 
+        /* message complete */
         if ((rx_bcnt -2) == rx_length) {
-            /* enable RS485 TX */
-            PORTD |= (1<<RXTX);
+            switch (rx_cmd) {
+                case CMD_WAIT:
+                case CMD_SWITCH_MODE:
+                    mpm_reply(rx_cmd, CAUSE_SUCCESS, 0, NULL);
+                    break;
 
-            /* first byte */
-            tx_cmd = rx_cmd;
-            UDR    = rx_cmd;
+                case CMD_GET_VERSION:
+                    mpm_reply(rx_cmd, CAUSE_SUCCESS, sizeof(versioninfo), (uint8_t *)versioninfo);
+                    break;
 
-            /* prepare header */
-            tx_bcnt   = 1;
-            tx_cause  = 0;
-            tx_length = 0;
+                case CMD_WRITE_RAW_COLOR:
+                case CMD_WRITE_INIT_COLOR:
+                case CMD_READ_RAW_COLOR:
+                case CMD_READ_INIT_COLOR:
+                    rx_ready = 1;
+                    break;
 
-            if (tx_cmd == CMD_GET_VERSION) {
-                tx_length = sizeof(versioninfo);
+                default:
+                    mpm_reply(rx_cmd, CAUSE_NOT_SUPPORTED, 0, NULL);
+                    break;
             }
-
-            /* enable interrupt */
-            UCSRB |= (1<<UDRIE);
         }
         rx_bcnt++;
     }
@@ -102,9 +145,8 @@ ISR(USART_UDRE_vect)
     sei();
 
     if ((tx_bcnt < 4) || (tx_bcnt -4) < tx_length) {
-        uint16_t pos = (tx_bcnt -4);
-        uint8_t data = 0xFF;
 
+        uint8_t data = 0xAA;
         if (tx_bcnt == 1) {
             data = tx_cause;
 
@@ -114,11 +156,8 @@ ISR(USART_UDRE_vect)
         } else if (tx_bcnt == 3) {
             data = (tx_length & 0xFF);
 
-        } else if (tx_cmd == CMD_GET_VERSION) {
-            data = versioninfo[pos];
-
-        } else {
-            data = 0xAA;
+        } else if ((tx_bcnt -4) < tx_length) {
+            data = tx_data[tx_bcnt -4];
         }
 
         UDR = data;
@@ -136,16 +175,105 @@ ISR(USART_TXC_vect, ISR_NOBLOCK)
     PORTD &= ~(1<<RXTX);
 
     /* enable MP mode again */
-    UCSRA |= (1<<MPCM);
-    rx_bcnt = 0xFF;     // FIXME: cli?
+    UCSRA  |= (1<<MPCM);
 
 #if !(STANDALONE)
-    if (tx_cmd == CMD_SWITCH_MODE) { // FIXME: check mode
+    /* reset MCU -> enter bootloader */
+    if ((tx_cmd == CMD_SWITCH_MODE) && (mpm_data[0] == BOOTMODE_BOOTLOADER)) {
         wdt_enable(WDTO_15MS);
     }
 #endif /* !(STANDALONE) */
 }
 
+static void mpm_reply(uint8_t cmd, uint8_t cause, uint16_t length, uint8_t *data)
+{
+    /* prepare header */
+    tx_cmd    = cmd;
+    tx_bcnt   = 1;
+    tx_cause  = cause;
+    tx_length = length;
+    tx_data   = data;
+
+    /* enable RS485 TX */
+    PORTD |= (1<<RXTX);
+
+    /* first byte and enable interrupt */
+    UDR    = tx_cmd;
+    UCSRB |= (1<<UDRIE);
+}
+
+void mpm_check_transfer(void)
+{
+    if (rx_ready == 0)
+        return;
+
+    rx_ready = 0;
+
+    switch (rx_cmd) {
+    case CMD_WRITE_RAW_COLOR:
+    case CMD_WRITE_INIT_COLOR:
+    {
+        uint8_t chan  = mpm_data[0];
+        uint8_t pos   = 1;
+        uint8_t cause = CAUSE_SUCCESS;
+
+        uint8_t (*baseptr)[3][16] = (rx_cmd == CMD_WRITE_RAW_COLOR) ? &chan_value : &nvram_data.initialRGB;
+
+        while ((pos < rx_length)) {
+            if ((chan >= 16) || ((pos +2) >= MPM_MAX_DATA_SIZE)) {
+                cause = CAUSE_INVALID_PARAMETER;
+                break;
+            }
+
+            baseptr[0][COLOR_RED][chan]   = mpm_data[pos++];
+            baseptr[0][COLOR_GREEN][chan] = mpm_data[pos++];
+            baseptr[0][COLOR_BLUE][chan]  = mpm_data[pos++];
+            chan++;
+        }
+
+        mpm_reply(rx_cmd, cause, 0, NULL);
+
+        if (rx_cmd == CMD_WRITE_RAW_COLOR) {
+            rgb_update(COLOR_MASK, 1);
+
+        } else {
+            eeprom_write();
+        }
+    }
+    break;
+
+    case CMD_READ_RAW_COLOR:
+    case CMD_READ_INIT_COLOR:
+    {
+        uint8_t chan  = mpm_data[0];
+        uint8_t count = mpm_data[1];
+        uint8_t pos   = 0;
+        uint8_t cause = CAUSE_SUCCESS;
+
+        uint8_t (*baseptr)[3][16] = (rx_cmd == CMD_READ_RAW_COLOR) ? &chan_value : &nvram_data.initialRGB;
+
+        while (count--) {
+            if ((chan >= 16) || ((pos +2) >= MPM_MAX_DATA_SIZE)) {
+                cause = CAUSE_INVALID_PARAMETER;
+                break;
+            }
+
+            mpm_data[pos++] = baseptr[0][COLOR_RED][chan];
+            mpm_data[pos++] = baseptr[0][COLOR_GREEN][chan];
+            mpm_data[pos++] = baseptr[0][COLOR_BLUE][chan];
+            chan++;
+        }
+
+        mpm_reply(rx_cmd, cause, pos, mpm_data);
+    }
+    break;
+
+    default:
+        mpm_reply(rx_cmd, CAUSE_UNSPECIFIED_ERROR, 0, NULL);
+        break;
+    }
+}
+
 void mpm_init(void)
 {
     PORTD &= ~(1<<RXTX);
diff --git a/rgb16mpm.h b/rgb16mpm.h
index 4fd7b27..63ae1dd 100644
--- a/rgb16mpm.h
+++ b/rgb16mpm.h
@@ -21,6 +21,8 @@
 #define MPM_ADDRESS     0x11
 #endif /* STANDALONE */
 
+#define VERSION_STRING  "rgb16mpm v0.99"
+
 #define COLOR_RED       0
 #define COLOR_GREEN     1
 #define COLOR_BLUE      2
@@ -47,6 +49,7 @@ void eeprom_read(void);
 
 /* mpmctrl.c funcs */
 void mpm_init(void);
+void mpm_check_transfer(void);
 
 /* rgbctrl.c vars */
 extern uint8_t chan_value[3][16];