diff --git a/Makefile b/Makefile
index f0fd549..62590da 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ CC_FLAGS = -mmcs51
 ASM = sdas8051
 AFLAGS= -plosgff
 
-all: rtlplayground.bin
+all: rtlplayground.bin injector
 
 SRCS= rtlplayground.c rtl837x_flash.c
 OBJS= ${SRCS:.c=.rel}
@@ -33,5 +33,8 @@ rtlplayground.ihx:  crtstart.rel $(OBJS)
 	echo "0000000: 00 40" | xxd -r - $@
 	cat $< >> $@
 
+injector: injector.c
+	gcc $^ -o $@
+
 .PHONY: clean all
 .PRECIOUS: %.rel %.ihx
diff --git a/rtl837x_regs.h b/rtl837x_regs.h
index ec51e14..a58974c 100644
--- a/rtl837x_regs.h
+++ b/rtl837x_regs.h
@@ -8,12 +8,29 @@
 // Defines the LED Mode for steering the Port LEDS and the System LED
 // BIT 17 set: LED solid on
 // Bytes 0/1 hold the LED mode, e.g. serial, RTL8231?
-#define RTL837X_REG_SMI_CTRL 0x6454
-#define RTL837X_REG_RESET 0x0024
-#define RTL837X_REG_SEC_COUNTER 0x06f4
-#define RTL837X_REG_SDS_MODES 0x7b20
-#define RTL837X_REG_LINKS 0x63f0
-
 // Blink rate is defined by setAsicRegBits(0x6520,0xe00000,rate);
 
+#define RTL837X_REG_SMI_CTRL 0x6454
+#define RTL837X_REG_RESET 0x0024
+// Writing 0x01 into this register causes a reset of the entire SoC
+#define RTL837X_REG_SEC_COUNTER 0x06f4
+// Used for counting seconds
+
+#define RTL837X_REG_SDS_MODES 0x7b20
+/*
+ * 5 Bits each give the state of the 2 SerDes of the RTL8372
+ * Values are:
+ * 0x1A: 10GBit USXGMII?
+ * 0x5: 2.5GBit: HISGMII ???
+ * 0x4: 1GBit: SGMII
+ */
+
+#define RTL837X_REG_LINKS 0x63f0
+/* Each nibble encodes the link state of a port.
+   Port 0 appears to be the CPU port
+   The RTL8372 serves ports 4-7, port 3 is the RTL8221
+   2: 1Gbit
+   5: 2.5Gbit
+  */
+
 #endif