diff --git a/SPIFlash.cpp b/SPIFlash.cpp
index 20d1960..72bb808 100644
--- a/SPIFlash.cpp
+++ b/SPIFlash.cpp
@@ -37,11 +37,16 @@ void SPIFlash::select() {
 }
 
 /// UNselect the flash chip
-void SPIFlash::unselect() {
+void SPIFlash::unselect(int us) {
   digitalWrite(_slaveSelectPin, HIGH);
+  if (us > 0) {
+    delayMicroseconds(us);
+  }
   interrupts();
 }
 
+
+
 /// setup SPI, read device ID etc...
 boolean SPIFlash::initialize()
 {
@@ -119,7 +124,7 @@ void SPIFlash::readBytes(long addr, void* buf, word len) {
 }
 
 /// Send a command to the flash chip, pass TRUE for isWrite when its a write command
-void SPIFlash::command(byte cmd, boolean isWrite){
+void SPIFlash::command(byte cmd, boolean isWrite, boolean busyWait){
 #if defined(__AVR_ATmega32U4__) // Arduino Leonardo, MoteinoLeo
   DDRB |= B00000001;            // Make sure the SS pin (PB0 - used by RFM12B on MoteinoLeo R1) is set as output HIGH!
   PORTB |= B00000001;
@@ -129,8 +134,13 @@ void SPIFlash::command(byte cmd, boolean isWrite){
     command(SPIFLASH_WRITEENABLE); // Write Enable
     unselect();
   }
-  while(busy()); //wait for any write/erase to complete
+
+  if (busyWait) {
+    while(busy()); //wait for any write/erase to complete
+  }
+
   select();
+
   SPI.transfer(cmd);
 }
 
@@ -216,16 +226,21 @@ void SPIFlash::blockErase32K(long addr) {
 }
 
 void SPIFlash::sleep() {
-  command(SPIFLASH_SLEEP); // Block Erase
+  command(SPIFLASH_SLEEP); // SLEEP
   unselect();
 }
 
 void SPIFlash::wakeup() {
-  command(SPIFLASH_WAKE); // Block Erase
-  unselect();
+  // not a write command
+  // do not wait for non-busy status because only SPIFLASH_WAKE command is accepted by the chip
+  // when in sleep mode
+  command(SPIFLASH_WAKE, false, false); 
+
+  // drive pin high for TRES1 microseconds
+  unselect(SPIFLASH_T_RES_1_US);
 }
 
 /// cleanup
 void SPIFlash::end() {
   SPI.end();
-}
\ No newline at end of file
+}
diff --git a/SPIFlash.h b/SPIFlash.h
index 20863c1..5df40fe 100644
--- a/SPIFlash.h
+++ b/SPIFlash.h
@@ -66,18 +66,19 @@
                                               // Example for Atmel-Adesto 4Mbit AT25DF041A: 0x1F44 (page 27: http://www.adestotech.com/sites/default/files/datasheets/doc3668.pdf)
                                               // Example for Winbond 4Mbit W25X40CL: 0xEF30 (page 14: http://www.winbond.com/NR/rdonlyres/6E25084C-0BFE-4B25-903D-AE10221A0929/0/W25X40CL.pdf)
 #define SPIFLASH_MACREAD          0x4B        // read unique ID number (MAC)
-                                              
+#define SPIFLASH_T_RES_1_US       3
+                         
 class SPIFlash {
 public:
   static byte UNIQUEID[8];
   SPIFlash(byte slaveSelectPin, uint16_t jedecID=0);
   boolean initialize();
-  void command(byte cmd, boolean isWrite=false);
+  void command(byte cmd, boolean isWrite=false, boolean busyWait=true);
   byte readStatus();
   byte readByte(long addr);
   void readBytes(long addr, void* buf, word len);
   void writeByte(long addr, byte byt);
-  void writeBytes(long addr, const void* buf, uint16_t len);
+  void writeBytes(long addr, const void* buf, uint16_t len); // len must be between 1-256
   boolean busy();
   void chipErase();
   void blockErase4K(long address);
@@ -90,9 +91,9 @@ class SPIFlash {
   void end();
 protected:
   void select();
-  void unselect();
+  void unselect(int us = 0);
   byte _slaveSelectPin;
   uint16_t _jedecID;
 };
 
-#endif
\ No newline at end of file
+#endif