diff --git a/avr.binary.tex b/avr.binary.tex
index e545745..3f7b69e 100644
--- a/avr.binary.tex
+++ b/avr.binary.tex
@@ -62,6 +62,7 @@
 }
 
 \newcommand{\avrloadc}[2][-Os -mmcu=atmega8]{%
+  \avr@init%
   \avr@compile{#2}{#1}%
   \avr@ihex@load{#2.hex}%
 }
diff --git a/avr.bitops.tex b/avr.bitops.tex
index 57d4b3d..638eb90 100644
--- a/avr.bitops.tex
+++ b/avr.bitops.tex
@@ -103,15 +103,22 @@
   \xdef#2{\@tmpa\@tmpa\@tmpa\@tmpa\@tmpa\@tmpa\@tmpa\@tmpa#1}%
 }
 
-\def\avr@bin@wtb@helper#1#2#3#4#5#6#7#8#9\@nnil{%
-  #9%
+\def\avr@bin@word@low#1#2{%
+  \edef\@tempa{#1}%
+  \edef#2{\expandafter\avr@bin@word@low@helper\@tempa\@nnil}%
+}
+\def\avr@bin@word@low@helper#1#2#3#4#5#6#7#8#9\@nnil{#9}
+
+\def\avr@bin@word@high#1#2{%
+  \edef\@tempa{#1}%
+  \edef#2{\expandafter\avr@bin@word@high@helper\@tempa\@nnil}%
+}
+\def\avr@bin@word@high@helper#1#2#3#4#5#6#7#8#9\@nnil{%
+  #1#2#3#4#5#6#7#8%
 }
 
 % \avr@bin@wtb bs:word, \result = ((uint8_t) bs)
-\def\avr@bin@wtb#1#2{%
-  \edef\@tempa{#1}%
-  \edef#2{\expandafter\avr@bin@wtb@helper\@tempa\@nnil}%
-}
+\def\avr@bin@wtb{\avr@bin@word@low}
 
 % \avr@bin@shiftleft bs:(byte|word), count, \result, \carry
 % -> \result = bs << count; \carry = (bs >> count) & 1
diff --git a/avr.instr.tex b/avr.instr.tex
index d074bb5..d94d576 100644
--- a/avr.instr.tex
+++ b/avr.instr.tex
@@ -3,14 +3,17 @@
 }
 
 \def\avr@error#1{%
-  \typeout{#1}\bye%
+  \errmessage{\the\avr@pc: #1}\bye%
 }
 
 
 % Execution Engine
 \def\avr@instr@step{%
   \avr@code@get{\avr@instr@current}%
-  %\avr@debug{\avr@instr@current}%
+  %\avr@reg@get{\csuse{avr@r24}}{\@@A}%
+  %\avr@reg@get{\csuse{avr@r28}}{\@@B}%
+  %\avr@reg@get{\csuse{avr@r29}}{\@@C}%
+  %\avr@debug{{r24=\@@A} {r28=\@@B} {r29=\@@C}}%
   % Dispatch Instruction by prefix
   \expandafter\avr@instr@dispatch\avr@instr@current\@nnil%
   \relax%
@@ -76,7 +79,9 @@
 % Match also from end for these prefixes
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \csdef{avr@instr@1001010}{\avr@instr@matchend{1001010}}
-
+% POP/PUSH
+\csdef{avr@instr@1001000}{\avr@instr@matchend{1001000}}
+\csdef{avr@instr@1001001}{\avr@instr@matchend{1001001}}
 
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -109,7 +114,6 @@
   \avr@reg@get{#2#3#4#5#6}{\avr@Rd}%
   \avr@debug{ADD - \%#2#3#4#5#6 <- #2#3#4#5#6 + \%#1#7}%
   \avr@debug{ADD - \avr@Rd <- \avr@Rd + \avr@Rr}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@id}%
   \csuse{avr@instr@adder@helper}%
   \avr@reg@set{\avr@Rx}{#2#3#4#5#6}%
   \avr@pc@inc%
@@ -124,7 +128,6 @@
   \avr@flag@get C \avr@instr@extracarry%
   \avr@debug{ADC - \%#2#3#4#5#6 <- #2#3#4#5#6 + \%#1#7}%
   \avr@debug{ADC - \avr@Rd <- \avr@Rd + \avr@Rr + \avr@instr@extracarry}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@id}%
   \csuse{avr@instr@adder@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{#2#3#4#5#6}%
@@ -139,8 +142,7 @@
   \def\avr@instr@extracarry{1}%
   \avr@debug{SUB - \%#2#3#4#5#6 <- #2#3#4#5#6 + \%#1#7}%
   \avr@debug{SUB - \avr@Rd <- \avr@Rd - \avr@Rr}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{#2#3#4#5#6}%
   \avr@pc@inc%
@@ -154,8 +156,7 @@
   \xdef \avr@instr@extracarry {\avr@bit@negate \@@carry}%
   \avr@debug{SBC - \%#2#3#4#5#6 <- #2#3#4#5#6 + \%#1#7}%
   \avr@debug{SBC - \avr@Rd <- \avr@Rd - \avr@Rr - \@@carry}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{#2#3#4#5#6}%
   \avr@pc@inc%
@@ -168,14 +169,13 @@
   \def\avr@Rr{#1#2#3#4#9}%
   \def\avr@instr@extracarry{1}%
   \avr@debug{SUBI - \%#2#3#4#5#6 <- #2#3#4#5#6(=\avr@Rd) - \avr@Rr}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{1#5#6#7#8}%
   \avr@pc@inc%
 }
 
-% SBCI - Substract Immediate
+% SBCI - Substract Immediate with Carry
 \def\avr@instr@SBCI{\avr@instr@gen@regconst{0100}}
 \csdef{avr@instr@0100}#1#2#3#4#5#6#7#8#9\@nnil{%
   \avr@reg@get{1#5#6#7#8}{\avr@Rd}%
@@ -183,8 +183,7 @@
   \avr@flag@get C \@@carry%
   \xdef \avr@instr@extracarry {\avr@bit@negate \@@carry}%
   \avr@debug{SBCI - \%#2#3#4#5#6 <- #2#3#4#5#6(=\avr@Rd) - \avr@Rr -\@@carry}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{1#5#6#7#8}%
   \avr@pc@inc%
@@ -197,8 +196,7 @@
   \avr@reg@get{#2#3#4#5#6}{\avr@Rd}%
   \def\avr@instr@extracarry{1}%
   \avr@debug{CP - #2#3#4#5#6(=\avr@Rd) - \%#1#7(=\avr@Rr)}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Do not set the output register
   \avr@pc@inc%
 }
@@ -211,8 +209,7 @@
   \avr@flag@get C \@@carry%
   \xdef \avr@instr@extracarry {\avr@bit@negate \@@carry}%
   \avr@debug{CP - #2#3#4#5#6(=\avr@Rd) - \%#1#7(=\avr@Rr)}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Do not set the output register
   \avr@pc@inc%
 }
@@ -223,10 +220,9 @@
   \avr@reg@get{1#5#6#7#8}{\avr@Rd}%
   \def\avr@Rr{#1#2#3#4#9}%
   \avr@flag@get C \@@carry%
-  \xdef \avr@instr@extracarry {\avr@bit@negate \@@carry}%
+  \xdef \avr@instr@extracarry{1}%
   \avr@debug{CPI - \%#2#3#4#5#6 <- #2#3#4#5#6(=\avr@Rd) - \avr@Rr -\@@carry}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@pc@inc%
 }
@@ -234,7 +230,6 @@
 \csdef{avr@instr@adder@helper}{%
   % Convert the Bitstring to Integer values
   \avr@bin@tocount{\avr@Rd}{\avr@accA}%
-  \avr@bin@map{\avr@instr@adder@RrPreprocess}{\avr@Rr}{\avr@Rr}%
   \avr@bin@tocount{\avr@Rr}{\avr@accB}%
   \advance \avr@accA by \avr@accB\relax%
   \advance \avr@accA by \avr@instr@extracarry\relax%
@@ -248,13 +243,14 @@
   \avr@bin@msb@get{\avr@Rr}{\@@R}%
   \avr@bin@msb@get{\avr@Rd}{\@@D}%
   \avr@bin@msb@get{\avr@Rx}{\@@X}%
+  \avr@debug{{Rr7:\@@R} {Rd7:\@@D} {R7:\@@X}}%
   % \avr@debug{R: \@@R D: \@@D X:\@@X}%
   \def\avr@ADD@carry{%
-    \@@or {\@@and \@@D {\@@not \@@X}}%
+    \@@or {\@@and \@@R \@@D}%
           {%
-            \@@or{\@@and \@@R \@@D}%
-                 {\@@and \@@R {\@@not \@@X}}}}%
-  \avr@flag@set C {\avr@instr@adder@RrPreprocess{\avr@ADD@carry}}%
+            \@@or{\@@and \@@R {\@@not \@@X}}%
+                 {\@@and \@@X {\@@not \@@D}}}}%
+  \avr@flag@set C {\avr@ADD@carry}%
   % Two's Complement Overflow
   \def\@@tmp{\@@or%
     {\@@and \@@D {\@@and \@@R {\@@not \@@X}}}%
@@ -269,11 +265,55 @@
           {%
             \@@or{\@@and \@@R \@@D}%
                  {\@@and \@@R {\@@not \@@X}}}}%
-  \avr@flag@set H {\avr@instr@adder@RrPreprocess{\avr@ADD@carry}}%
+  \avr@flag@set H {\avr@ADD@carry}%
   %% Update Dependend Flags (N, Z, S)
   \avr@flags@update \avr@Rx%
 }
 
+\csdef{avr@instr@subber@helper}{%
+  % Convert the Bitstring to Integer values
+  \avr@bin@tocount{\avr@Rd}{\avr@accA}%
+  \avr@bin@negate{\avr@Rr}{\@@Rr}%
+  \avr@bin@tocount{\@@Rr}{\avr@accB}%
+  \advance \avr@accA by \avr@accB\relax%
+  \advance \avr@accA by \avr@instr@extracarry\relax%
+  \avr@count@modulo@byte{\avr@accA}%
+  \avr@count@tobin@b{\avr@accA}{\avr@Rx}%
+  % Calculate the Flags
+  \let\@@not=\avr@bit@negate%
+  \let\@@and=\avr@bit@and%
+  \let\@@or=\avr@bit@or%
+  %% Carry
+  \avr@bin@msb@get{\avr@Rr}{\@@R}%
+  \avr@bin@msb@get{\avr@Rd}{\@@D}%
+  \avr@bin@msb@get{\avr@Rx}{\@@X}%
+  \avr@debug{{Rr7:\@@R} {Rd7:\@@D} {R7:\@@X}}%
+  \def\avr@ADD@carry{%
+    \@@or {\@@and {\@@not \@@D} \@@R}%
+          {%
+            \@@or{\@@and \@@R \@@X}%
+                 {\@@and \@@X {\@@not \@@D}}}}%
+  \avr@flag@set C {\avr@ADD@carry}%
+  % Two's Complement Overflow
+  \def\@@tmp{\@@or%
+    {\@@and \@@D {\@@and {\@@not \@@R} {\@@not \@@X}}}%
+    {\@@and {\@@not \@@D} {\@@and \@@R \@@X}}}%
+  \avr@flag@set V \@@tmp%
+  % Half Carry
+  \avr@bin@getbit{\avr@Rr}{3}{\@@R}%
+  \avr@bin@getbit{\avr@Rd}{3}{\@@D}%
+  \avr@bin@getbit{\avr@Rx}{3}{\@@X}%
+  \def\avr@ADD@carry{%
+    \@@or {\@@and {\@@not \@@D} \@@R}%
+          {%
+            \@@or{\@@and \@@R \@@X}%
+                 {\@@and \@@X {\@@not \@@D}}}}%
+  \avr@flag@set H {\avr@ADD@carry}%
+  %% Update Dependend Flags (N, Z, S)
+  \avr@flags@update \avr@Rx%
+}
+
+
 % LDI -- Load Immediate Value
 \def\avr@instr@LDI{\avr@instr@gen@regconst{1110}}
 \def\avr@instr@SER#1#2{\avr@instr@gen@regconst{1110}{#1}{#2}{11111111}}
@@ -308,6 +348,16 @@
   #2=\avr@count@tmpa\relax%
 }
 
+\def\avr@instr@rjump@dec#1#2{%
+  \avr@bin@tocount{0000#1}{\avr@count@tmpa}%
+  \ifnum \avr@count@tmpa > 2047%
+     \avr@count@tmpb=\avr@count@tmpa%
+     \avr@count@tmpa=-4096%
+     \advance \avr@count@tmpa by \avr@count@tmpb\relax%
+  \fi%
+  #2=\avr@count@tmpa\relax%
+}
+
 % BRBC -- Branch if Bit in SREG is cleared
 \def\avr@instr@BRBC#1#2#3{% ADD PC, Bit, Offset
   \avr@instr@jump@enc{#3}{\@@offset}%
@@ -417,6 +467,52 @@
   \avr@pc@inc%
 }
 
+% RJMP
+% #1 = Offset 
+% FIXME latex assembler
+\csdef{avr@instr@1100}#1\@nnil{
+  \avr@instr@rjump@dec{#1}{\avr@count@tmpa}%
+  \avr@debug{RJMP \the\avr@count@tmpa}%
+  \avr@pc@add{\avr@count@tmpa}%
+  \avr@pc@inc%
+}
+
+% RCALL
+\csdef{avr@instr@1101}#1\@nnil{
+  \avr@count@tobin@w{\the\avr@pc}{\@@pc}%
+  \avr@instr@rjump@dec{#1}{\avr@count@tmpa}%
+  \avr@reg@get{\csuse{avr@r24}}{\@@A}%
+  \avr@reg@get{\csuse{avr@r25}}{\@@B}%
+  \avr@reg@get{\csuse{avr@r26}}{\@@C}%
+  \avr@debug{RCALL \the\avr@count@tmpa {r24:\@@A} {r25:\@@B} {r26:\@@C}}%
+  \avr@pc@add{\avr@count@tmpa}%
+  \avr@bin@word@low{\@@pc}{\@@low}%
+  \avr@bin@word@high{\@@pc}{\@@high}%
+  \avr@mem@set{\@@low}{\the\avr@stackptr}%
+  \advance\avr@stackptr by -1\relax%
+  \avr@mem@set{\@@high}{\the\avr@stackptr}%
+  \advance\avr@stackptr by -1\relax%
+  \avr@pc@inc%
+  \avr@debug{  done}%
+}
+
+% RET
+\def\avr@instr@RET#1{%
+  \avr@code@set{1001010100001000}{#1}%
+}
+\csdef{avr@instr@1001010100001000}\@nnil{%
+  \avr@reg@get{\csuse{avr@r24}}{\@@X}%
+  \avr@debug{RET (r24=\@@X)}%
+  \advance\avr@stackptr by 1\relax
+  \avr@mem@get{\the\avr@stackptr}{\@@high}%
+  \advance\avr@stackptr by 1\relax
+  \avr@mem@get{\the\avr@stackptr}{\@@low}%
+  \avr@bin@tocount{\@@high \@@low}{\avr@pc}%
+  \avr@pc@inc\relax%
+  \avr@debug{  done }%
+}
+
+
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Data transfert instructions
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -444,6 +540,30 @@
   \avr@pc@inc%
 }
 
+% PUSH
+\def\avr@instr@PUSH#1#2{% PC, Reg
+  \avr@code@set{1001001#21111}{#1}%
+}
+
+\csdef{avr@instr@1001001:1111}#1\@nnil{%
+  \avr@reg@get{#1}{\avr@Rr}%
+  \avr@debug{PUSH #1(=\avr@Rr)}%
+  \avr@mem@set{\avr@Rr}{\the\avr@stackptr}%
+  \advance\avr@stackptr by -1\relax%
+  \avr@pc@inc%
+}
+
+% POP
+\def\avr@instr@POP#1#2{% PC, Reg
+  \avr@code@set{1001000#21111}{#1}%
+}
+\csdef{avr@instr@1001000:1111}#1\@nnil{%
+  \advance\avr@stackptr by 1\relax%
+  \avr@debug{POP #1}%
+  \avr@mem@get{\the\avr@stackptr}{\avr@Rr}%
+  \avr@reg@set{\avr@Rr}{#1}%
+  \avr@pc@inc%
+}
 
 
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
@@ -615,8 +735,7 @@
   \avr@debug{NEG: #1(=\avr@Rr)}%
   \def\avr@Rd{00000000}%
   \def\avr@instr@extracarry{1}%
-  \def\avr@instr@adder@RrPreprocess{\avr@bit@negate}%
-  \csuse{avr@instr@adder@helper}%
+  \csuse{avr@instr@subber@helper}%
   % Set the result register
   \avr@reg@set{\avr@Rx}{#1}%
   \avr@pc@inc%
diff --git a/avr.memory.tex b/avr.memory.tex
index b83d539..cee4fab 100644
--- a/avr.memory.tex
+++ b/avr.memory.tex
@@ -5,6 +5,7 @@
   \avr@flag@init%
   \avr@reg@init%
   \avr@pc@init%
+  \avr@stack@init%
 }
 
 \newcount\avr@accA
@@ -94,8 +95,8 @@
 
 \def\avr@flags@update#1{%
   % Negate Flag
-  \avr@bin@msb@get{#1}{\@@X}%
-  \avr@flag@set N \@@X%
+  \avr@bin@msb@get{#1}{\@@N}%
+  \avr@flag@set N \@@N%
   % Zero Flag
   \avr@bin@tocount{#1}{\avr@count@tmpa}%
   \ifnum \avr@count@tmpa = 0%
@@ -105,8 +106,8 @@
   \fi%
   % Signed Flag
   \avr@flag@get V \@@V%
-  \edef\@@tmp{\avr@bit@xor \@@X \@@V}%
-  \avr@flag@set S \@@V%
+  \edef\@@tmp{\avr@bit@xor \@@N \@@V}%
+  \avr@flag@set S \@@tmp%
 }
 
 %% Registers
@@ -211,6 +212,47 @@
   \csxdef{avr@code@#2}{#1}%
 }
 %% RAM
+\newcount\avr@stackptr
+\def\avr@stack@init{
+  \avr@stackptr=0%
+}
+
+\def\avr@stack@SPL@get#1{%
+  \avr@count@tobin@w{\avr@stackptr}{\@@stack}%
+  \avr@bin@word@low{\@@stack}{#1}%
+}
+\def\avr@stack@SPH@get#1{%
+  \avr@count@tobin@w{\avr@stackptr}{\@@stack}%
+  \avr@bin@word@high{\@@stack}{#1}%
+}
+
+\def\avr@stack@SPL@set#1{%
+  \avr@count@tobin@w{\avr@stackptr}{\@@stack}%
+  \avr@bin@word@high{\@@stack}{\@@high}%
+  \avr@bin@tocount{\@@high #1}{\avr@stackptr}%
+  \avr@debug{  SP=\the\avr@stackptr}
+}
+
+\def\avr@stack@SPH@set#1{%
+  \avr@count@tobin@w{\avr@stackptr}{\@@stack}%
+  \avr@bin@word@low{\@@stack}{\@@low}%
+  \avr@bin@tocount{#1\@@low}{\avr@stackptr}%
+  \avr@debug{  SP=\the\avr@stackptr}
+}
+
+\def\avr@mem@set#1#2{% Bitstring, Address (as number)
+  \avr@debug{  MEM W *#2=#1}%
+  \csxdef{avr@mem@#2}{#1}%
+}
+
+\def\avr@mem@get#1#2{% Address (as number), Target Macro
+  \ifcsdef{avr@mem@#1}{%
+    \edef#2{\csuse{avr@mem@#1}}%
+  }{%
+    \edef#2{00000000}%
+  }%
+  \avr@debug{  MEM R *#1==#2}%
+}
 
 
 %%% Local Variables: 
diff --git a/avr.testsuite.tex b/avr.testsuite.tex
index a672f5d..fd52238 100644
--- a/avr.testsuite.tex
+++ b/avr.testsuite.tex
@@ -87,7 +87,7 @@
 
   \avr@test@helper{00001111}{00010000}%
   \avr@test@REG{r17}{11111111}%
-  \avr@test@SREG{00000101}%
+  \avr@test@SREG{00010101}%
 }
 \appto\avr@test{\avr@test@SUB}
 
@@ -110,7 +110,7 @@
   \avr@test@helper{00000000}{00000000}{00000000}{00000001}%
   \avr@test@REG{r17}{11111111}%
   \avr@test@REG{r18}{11111111}%
-  \avr@test@SREG{00100101}%
+  \avr@test@SREG{00110101}%
 
   \avr@test@helper{00000000}{10000000}{00000000}{00000001}%
   \avr@test@REG{r17}{00000000}%
@@ -204,11 +204,11 @@
 
   \avr@instr@stepn{2}%
   \avr@test@REG{r30}{11111111}
-  \avr@test@SREG{00000101}
+  \avr@test@SREG{00010101}
 
   \avr@instr@stepn{1}%
   \avr@test@REG{r30}{11111101}
-  \avr@test@SREG{00000100}
+  \avr@test@SREG{00010100}
 }
 \preto\avr@test{\avr@test@SUBI}
 
@@ -279,7 +279,7 @@
 
   \avr@instr@stepn{2}%
   \avr@test@REG{r20}{11111111}
-  \avr@test@SREG{00100101}
+  \avr@test@SREG{00110101}
 
   \avr@instr@stepn{1}%
   \avr@test@REG{r20}{00000001}
@@ -296,7 +296,7 @@
 
   \avr@instr@stepn{2}%
   \avr@test@REG{r20}{11111110}
-  \avr@test@SREG{00000101}
+  \avr@test@SREG{00010101}
 
   \avr@instr@stepn{1}%
   \avr@test@REG{r20}{00000001}
@@ -336,7 +336,7 @@
 
   \avr@instr@stepn{2}%
   \avr@test@REG{r20}{11000100}
-  \avr@test@SREG{00000101}
+  \avr@test@SREG{00010101}
 }
 \preto\avr@test{\avr@test@ASR}
 
@@ -372,7 +372,7 @@
 
   \avr@instr@stepn{1}%
   \avr@test@REG{r20}{10000000}
-  \avr@test@SREG{00011100}
+  \avr@test@SREG{00001100}
 
   \avr@instr@stepn{1}%
   \avr@test@REG{r20}{01000000}
@@ -385,11 +385,64 @@ int main() { }
 \end{filecontents*}
 
 \def\avr@test@emptymain{%
+  \avr@test@setup{Empty Main Function}%
   \avrloadc{empty-main.c}
-  \avr@instr@stepn{3}
+  \avr@instr@stepn{50}
 }
 \preto\avr@test{\avr@test@emptymain}
 
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{filecontents*}{sum-rec.c}
+#include <avr/io.h>
+
+char sum(char n) {
+  if (n <= 1) {
+    return n;
+  }
+  return n + sum(n-1);
+}
+
+int main() { 
+  UDR = sum(4);
+  asm volatile ("break");
+}
+\end{filecontents*}
+
+\def\avr@test@sumRec{%
+  \avr@test@setup{Summing Recursive}%
+  \avrloadc{sum-rec.c}
+  \avr@instr@stepn{1000}
+  \avr@test@REG{r24}{00001010}
+}
+
+\preto\avr@test{\avr@test@sumRec}
+
+%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
+\begin{filecontents*}{fibonacci-rec.c}
+#include <avr/io.h>
+
+char fib(char n) {
+  if (n <= 1) {
+    return 1;
+  }
+  return fib(n-1) + fib(n-2);
+}
+
+int main() { 
+  UDR = fib(5);
+  asm volatile ("break");
+}
+\end{filecontents*}
+
+\def\avr@test@fibRec{%
+  \avr@test@setup{Fibonacci Recursive}%
+  \avrloadc{fibonacci-rec.c}
+  \avr@instr@stepn{1000}
+  \avr@test@REG{r24}{00001000}
+}
+\preto\avr@test{\avr@test@fibRec}
+
+
 
 %%% Local Variables: 
 %%% mode: latex
diff --git a/avr.tex b/avr.tex
index 47556b6..dff803c 100644
--- a/avr.tex
+++ b/avr.tex
@@ -15,6 +15,7 @@
 \input{avr.bitops}
 \input{avr.memory}
 \input{avr.instr}
+\input{avr.io}
 \input{avr.testsuite}