diff --git a/assets/serialtest.js b/assets/serialtest.js
index c795c4d..726ddcf 100644
--- a/assets/serialtest.js
+++ b/assets/serialtest.js
@@ -2,6 +2,7 @@ var ba = com.sendMessageGetBytes(0, "DEVNAM"+String.fromCharCode(0x17));
 serial.println(ba);
 
 ba = com.pullMessage(0)
-serial.println(ba);
+serial.print(ba);
+serial.println("# END OF MSG");
 
-serial.println("\nk bye")
\ No newline at end of file
+serial.println("k bye")
\ No newline at end of file
diff --git a/serialdev.txt b/serialdev.txt
index b9cf02e..22d88c3 100644
--- a/serialdev.txt
+++ b/serialdev.txt
@@ -85,18 +85,19 @@ Description: opens the file for writing
 
 Description: opens the file for appending (a variant of write)
 
-    WRITE<number of bytes to write>
+    WRITE
 
-Description: puts the device to WRITE mode. Any subsequent bytes will be interpreted as-is for writing
+Description: puts the device into WRITE mode. Any subsequent bytes will be interpreted as-is for writing
 
     FLUSH
 
 Description: flushes any internal output buffer and no longer puts the device to WRITE mode
 
-    READ<number of bytes to read>
+    READ
 
-Description: reads specified number of bytes. Any subsequent reading operation will return bytes stored into the file
-             until the specified number of bytes reached
+Description: reads one block of file. Any subsequent read attempts will return next block. If file size is lesser
+             than a single block, rest of the bytes will be filled with zero, and size-of-the-block (see terranmon.txt)
+             will be set accordingly.
 
     CLOSE
 
diff --git a/src/net/torvald/tsvm/peripheral/TestDiskDrive.kt b/src/net/torvald/tsvm/peripheral/TestDiskDrive.kt
index 7158412..54297e5 100644
--- a/src/net/torvald/tsvm/peripheral/TestDiskDrive.kt
+++ b/src/net/torvald/tsvm/peripheral/TestDiskDrive.kt
@@ -55,6 +55,8 @@ class TestDiskDrive(private val driveNum: Int) : BlockTransferInterface(false, t
     private var file: File? = null
     //private var readModeLength = -1 // always 4096
     private var stateCode = STATE_CODE_STANDBY
+    private var writeMode = false
+    private var writeModeLength = -1
 
     private val messageComposeBuffer = ByteArrayOutputStream(BLOCK_SIZE) // always use this and don't alter blockSendBuffer please
     private var blockSendBuffer = ByteArray(1)
@@ -92,14 +94,12 @@ class TestDiskDrive(private val driveNum: Int) : BlockTransferInterface(false, t
                 blockSendBuffer = messageComposeBuffer.toByteArray()
             }
 
-            recipient.writeout(ByteArray(BLOCK_SIZE) {
-                val i = blockSendCount * BLOCK_SIZE
-                if (i + it >= blockSendBuffer.size) {
-                    0.toByte()
-                }
-                else {
-                    blockSendBuffer[i + it]
-                }
+            val sendSize = if (blockSendBuffer.size - (blockSendCount * BLOCK_SIZE) < BLOCK_SIZE)
+                blockSendBuffer.size % BLOCK_SIZE
+            else BLOCK_SIZE
+
+            recipient.writeout(ByteArray(sendSize) {
+                blockSendBuffer[blockSendCount * BLOCK_SIZE + it]
             })
 
             blockSendCount += 1
@@ -124,21 +124,20 @@ class TestDiskDrive(private val driveNum: Int) : BlockTransferInterface(false, t
             file = null
             blockSendCount = 0
             stateCode = STATE_CODE_STANDBY
+            writeMode = false
+            writeModeLength = -1
         }
         else if (inputString.startsWith("DEVSTU$END_OF_SEND_BLOCK")) {
             if (stateCode < 128) {
                 recipient?.writeout(composePositiveAns("${stateCode.toChar()}", errorMsgs[stateCode]))
-                //startSend { it.writeout(composePositiveAns("${stateCode.toChar()}", errorMsgs[stateCode])) }
             }
             else {
-                startSend { it.writeout(composeNegativeAns("${stateCode.toChar()}", errorMsgs[stateCode])) }
+                recipient?.writeout(composeNegativeAns("${stateCode.toChar()}", errorMsgs[stateCode]))
             }
         }
         else if (inputString.startsWith("DEVTYP$END_OF_SEND_BLOCK"))
-            //startSend { it.writeout(composePositiveAns("STOR")) }
             recipient?.writeout(composePositiveAns("STOR"))
         else if (inputString.startsWith("DEVNAM$END_OF_SEND_BLOCK"))
-            //startSend { it.writeout(composePositiveAns("Testtec Virtual Disk Drive")) }
             recipient?.writeout(composePositiveAns("Testtec Virtual Disk Drive"))
         else if (inputString.startsWith("OPENR\"") || inputString.startsWith("OPENW\"") || inputString.startsWith("OPENA\"")) {
             if (file != null) {
diff --git a/src/net/torvald/tsvm/peripheral/TestFunctionGenerator.kt b/src/net/torvald/tsvm/peripheral/TestFunctionGenerator.kt
index ac7ac66..cea3c1d 100644
--- a/src/net/torvald/tsvm/peripheral/TestFunctionGenerator.kt
+++ b/src/net/torvald/tsvm/peripheral/TestFunctionGenerator.kt
@@ -80,7 +80,8 @@ Nunc mollis nibh vitae sapien consequat, ut vestibulum sem pharetra. Aliquam iac
 15360th Byte 000111111111111111122222222222222223333333333333333444444444444444455555555555555556666666666666666777777777777777788888888888888889999999999999999AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFF
 15616th Byte 000111111111111111122222222222222223333333333333333444444444444444455555555555555556666666666666666777777777777777788888888888888889999999999999999AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFF
 15872nd Byte 000111111111111111122222222222222223333333333333333444444444444444455555555555555556666666666666666777777777777777788888888888888889999999999999999AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFF
-16128th Byte 000111111111111111122222222222222223333333333333333444444444444444455555555555555556666666666666666777777777777777788888888888888889999999999999999AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFF#""".toByteArray(Charsets.US_ASCII)
+16128th Byte 000111111111111111122222222222222223333333333333333444444444444444455555555555555556666666666666666777777777777777788888888888888889999999999999999AAAAAAAAAAAAAAAABBBBBBBBBBBBBBBBCCCCCCCCCCCCCCCCDDDDDDDDDDDDDDDDEEEEEEEEEEEEEEEEFFFFFFFFFFFFFFF
+16384th Byte and some trailing bytes too!""".toByteArray(Charsets.US_ASCII)
 
     private var fileOpen = false
 
@@ -106,14 +107,12 @@ Nunc mollis nibh vitae sapien consequat, ut vestibulum sem pharetra. Aliquam iac
                 blockSendBuffer = fileContent_multiblocks
             }
 
-            recipient.writeout(ByteArray(BLOCK_SIZE) {
-                val i = blockSendCount * BLOCK_SIZE
-                if (i + it >= blockSendBuffer.size) {
-                    0.toByte()
-                }
-                else {
-                    blockSendBuffer[i + it]
-                }
+            val sendSize = if (blockSendBuffer.size - (blockSendCount * BLOCK_SIZE) < BLOCK_SIZE)
+                blockSendBuffer.size % BLOCK_SIZE
+            else BLOCK_SIZE
+
+            recipient.writeout(ByteArray(sendSize) {
+                blockSendBuffer[blockSendCount * BLOCK_SIZE + it]
             })
 
             blockSendCount += 1