diff --git a/programmer_protocol.h b/programmer_protocol.h
new file mode 100644
index 0000000..4d11149
--- /dev/null
+++ b/programmer_protocol.h
@@ -0,0 +1,118 @@
+/*
+ * programmer_protocol.h
+ *
+ *  Created on: Dec 26, 2011
+ *      Author: Doug
+ */
+
+#ifndef PROGRAMMER_PROTOCOL_H_
+#define PROGRAMMER_PROTOCOL_H_
+
+// When the programmer is in "waiting for command" mode,
+// you send it one of the bytes below to do something (or begin to do something)
+typedef enum ProgrammerCommand
+{
+	EnterWaitingMode = 0,
+	DoElectricalTest,
+	IdentifyChips,
+	ReadByte,
+	ReadChips,
+	EraseChips,
+	WriteChips,
+	GetBootloaderState,
+	EnterBootloader,
+	EnterProgrammer,
+	BootloaderEraseAndWriteProgram
+} ProgrammerCommand;
+
+// After a command is sent, the programmer will always respond with
+// one of the replies below. (Depending on the command, it may reply with other
+// stuff after that, too)
+typedef enum ProgrammerReply
+{
+	CommandReplyOK = 0,
+	CommandReplyError,
+	CommandReplyInvalid
+} ProgrammerReply;
+
+// -------------------------  ELECTRICAL TEST PROTOCOL  -------------------------
+// After CommandReplyOK, any failures are reported by the programmer.
+// It will send ProgrammerElectricalTestFail followed by two more bytes -- each
+// representing an index of the failure location. Any more electrical test failures
+// will result in another 3-byte sequence as described above.
+// When it's totally finished, it will send ProgrammerElectricalTestDone.
+// So a pass would be indicated by no ProgrammerElectricalTestFail sequences being
+// sent.
+typedef enum ProgrammerElectricalTestReply
+{
+	ProgrammerElectricalTestFail = 0,
+	ProgrammerElectricalTestDone
+} ProgrammerElectricalTestReply;
+
+// -------------------------  IDENTIFY CHIPS PROTOCOL  -------------------------
+// After CommandReplyOK, it will send the manufacturer ID and device ID of each
+// of the 4 chips:
+// M1, D1, M2, D2, M3, D3, M4, D4
+// followed by ProgrammerIdentifyDone.
+typedef enum ProgrammerIdentifyReply
+{
+	ProgrammerIdentifyDone = 0
+} ProgrammerIdentifyReply;
+
+// -------------------------  READ PROTOCOL  -------------------------
+// After CommandReplyOK, the programmer will send a chunk of data.
+// The computer will send a reply (see the enum below this one)
+// The programmer will then reply to *that* reply (see this enum)
+typedef enum ProgrammerReadReply
+{
+	ProgrammerReadOK = 0,
+	ProgrammerReadError,
+	ProgrammerReadMoreData,
+	ProgrammerReadFinished,
+	ProgrammerReadConfirmCancel
+} ProgrammerReadReply;
+
+// When the computer is confirming reception of a block of data from the device,
+// it should reply with either OK that it received the data OK, or cancel
+// to tell the device that the user canceled the read.
+typedef enum ComputerReadReply
+{
+	ComputerReadOK = 0,
+	ComputerReadCancel
+} ComputerReadReply;
+
+// -------------------------  ERASE PROTOCOL  -------------------------
+// There is none -- a reply of CommandReplyOK will indicate that the erase
+// completed successfully.
+
+// -------------------------  WRITE PROTOCOL  -------------------------
+// After CommandReplyOK, the computer should send one of the commands below.
+// The programmer will reply with one of the replies seen in the enum below
+// this one, and then the computer can send a 1024-byte chunk of data.
+// The programmer will reply with ProgrammerWriteOK, and then the cycle can
+// continue (the computer sends another request in this enum)
+typedef enum ComputerWriteRequest
+{
+	ComputerWriteMore = 0,
+	ComputerWriteFinish,
+	ComputerWriteCancel
+} ComputerWriteRequest;
+
+typedef enum ProgrammerWriteReply
+{
+	ProgrammerWriteOK = 0,
+	ProgrammerWriteError,
+	ProgrammerWriteConfirmCancel
+} ProgrammerWriteReply;
+
+// -------------------------  BOOTLOADER STATE PROTOCOL  -------------------------
+// If the command is GetBootloaderState, it will reply with CommandReplyOK followed
+// by one of the two replies below to tell the control program which mode
+// the device is currently in.
+typedef enum BootloaderStateReply
+{
+	BootloaderStateInBootloader = 0,
+	BootloaderStateInProgrammer
+} BootloaderStateReply;
+
+#endif /* PROGRAMMER_PROTOCOL_H_ */
diff --git a/usb_serial/usb_serial.c b/usb_serial/usb_serial.c
index 150dfe9..5687fa3 100644
--- a/usb_serial/usb_serial.c
+++ b/usb_serial/usb_serial.c
@@ -10,6 +10,7 @@
 #include "../Descriptors.h"
 #include "../external_mem.h"
 #include "../tests/simm_electrical_test.h"
+#include "../programmer_protocol.h"
 
 #define CHIP_SIZE					(512UL * 1024UL)
 #define READ_CHUNK_SIZE_BYTES		1024UL
@@ -55,73 +56,6 @@ typedef enum ProgrammerCommandState
 	WritingChips
 } ProgrammerCommandState;
 
-typedef enum ProgrammerCommand
-{
-	EnterWaitingMode = 0,
-	DoElectricalTest,
-	IdentifyChips,
-	ReadByte,
-	ReadChips,
-	EraseChips,
-	WriteChips,
-	GetBootloaderState,
-	EnterBootloader,
-	EnterProgrammer
-} ProgrammerCommand;
-
-typedef enum ProgrammerReply
-{
-	CommandReplyOK = 0,
-	CommandReplyError,
-	CommandReplyInvalid
-} ProgrammerReply;
-
-typedef enum BootloaderStateReply
-{
-	BootloaderStateInBootloader = 0,
-	BootloaderStateInProgrammer
-} BootloaderStateReply;
-
-typedef enum ComputerReadReply
-{
-	ComputerReadOK = 0,
-	ComputerReadCancel
-} ComputerReadReply;
-
-typedef enum ProgrammerReadReply
-{
-	ProgrammerReadOK = 0,
-	ProgrammerReadError,
-	ProgrammerReadMoreData,
-	ProgrammerReadFinished,
-	ProgrammerReadConfirmCancel
-} ProgrammerReadReply;
-
-typedef enum ComputerWriteReply
-{
-	ComputerWriteMore = 0,
-	ComputerWriteFinish,
-	ComputerWriteCancel
-} ComputerWriteReply;
-
-typedef enum ProgrammerWriteReply
-{
-	ProgrammerWriteOK = 0,
-	ProgrammerWriteError,
-	ProgrammerWriteConfirmCancel
-} ProgrammerWriteReply;
-
-typedef enum ProgrammerIdentifyReply
-{
-	ProgrammerIdentifyDone = 0
-} ProgrammerIdentifyReply;
-
-typedef enum ProgrammerElectricalTestReply
-{
-	ProgrammerElectricalTestFail = 0,
-	ProgrammerElectricalTestDone
-} ProgrammerElectricalTestReply;
-
 static ProgrammerCommandState curCommandState = WaitingForCommand;
 static uint8_t byteAddressReceiveCount = 0;
 static uint16_t curReadIndex;
@@ -248,6 +182,7 @@ void USBSerial_HandleWaitingForCommandByte(uint8_t byte)
 	switch (byte)
 	{
 	case EnterWaitingMode:
+		SendByte(CommandReplyOK);
 		curCommandState = WaitingForCommand;
 		break;
 	case DoElectricalTest: