Turned the whole thing into a modpack.

modpack.txt

@@ -0,0 +1 @@
+The presence of this file indicates that the current folder is a modpack.

t400/init.lua

@@ -1,7 +1,11 @@
+if not digiline then
+ print("Digilines not found.")
+ return
+end
 local oldprint=print
 local function print(...)
  for k,v in ipairs({...}) do
-  oldprint("[Test3D] "..tostring(v))
+  oldprint("[Test3D:T400] "..tostring(v))
  end
 end
 print("Test3D loading.")
@@ -10,15 +14,9 @@ local tInstructions = {
 "NOP",
 "ADD",
 "SUB",
+"PEEK",
+"POKE",
 }
---[[
-local statedir = minetest.get_worldpath() .. '/' .. minetest.get_current_modname() .. "/"
-print("State directory: "..statedir)
-if not digiline then
- print("Digilines not found.")
- return
-end
-]]--
 local function push(pos,val)
  local meta = minetest.get_meta(pos)
  local sstack = ""
@@ -43,43 +41,46 @@ local function pop(pos)
  end
  return tonumber(n)
 end
-local function t21_digiline_receive(pos, node, channel, msg)
+local function t400_digiline_receive(pos, node, channel, msg)
  print(pos,node,channel,msg)
  meta = minetest.get_meta(pos)
- if meta:get_string("state") == "waiting" and meta:get_string("waitingfor") == channel then
+ if meta:get_string("waitingfor") == channel then
+  if meta:get_string("state") == "waitingstack" then
    push(pos,msg)
+  if meta:get_string("state") == "waitingins" then
+   meta:set_int("ci",tonumber(msg))
   end
  end
-print("Created T21 digiline function")
+end
+print("Created T400 digiline function")
 
-local function t21_set_infotext(pos)
+local function t400_set_infotext(pos)
  local meta=minetest.get_meta(pos)
  local running="false"
  if meta:get_int("test3d_running") == 1 then running="true" end
  meta:set_string("infotext","Running: "..running.."\nState: "..meta:get_string("state").."\nPC: "..tostring(meta:get_int("pc")).."\nACC: "..tostring(meta:get_int("acc")).."\nBAK: "..tostring(meta:get_int("bak")))
 end
 
-local function t21_set_meta(pos)
+local function t400_set_meta(pos)
  local meta = minetest.get_meta(pos)
- local fspec = "size[8,9]\nlabel[0,0;T21 execution node]\nfield[0.25,1;8,1;channel;Channel prefix;${channel}]\n"
+ local fspec = "size[8,9]\nlabel[0,0;T400 execution node]\nfield[0.25,1;8,1;channel;Channel prefix;${channel}]\n"
  fspec = fspec .. "textarea[0.25,2;8,7.5;program;Program;${program}]\n"
  fspec = fspec .. "button_exit[0,8.5;7.9,1;;Done]\n"
  meta:set_string("formspec",fspec)
  meta:set_string("channel","")
- meta:set_string("program","#This is the default program.")
- meta:set_string("state","running") -- can be "running", or "waiting"
+ meta:set_string("state","running") -- can be "running", "waitingstack" or "waitingins"
  meta:set_string("waitingfor","") -- address waiting for
- meta:set_int("pc",0)
- meta:set_int("acc",0)
- meta:set_int("bak",0)
- t21_set_infotext(pos)
- print("Initialized T21 at "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z))
+ meta:set_string("stack","") -- internal stack
+ meta:set_int("ci",0) -- current instruction
+ meta:set_int("pc",0) -- program counter
+ t400_set_infotext(pos)
+ print("Initialized T400 at "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z))
 end
-minetest.register_node("test3d:t21", {
- description = "T21 Execution Node",
+minetest.register_node("test3d:t400", {
+ description = "T400 Execution Node",
  tiles = {
   {
-   image="t21.png",
+   image="t400.png",
    animation={
     type = "vertical_frames",
     aspect_w=16,
@@ -89,7 +90,7 @@ minetest.register_node("test3d:t21", {
    },
   },
  },
- on_construct = t21_set_meta,
+ on_construct = t400_set_meta,
  on_punch = function(pos, _, _, _)
   local meta=minetest.get_meta(pos)
   local cstate = meta:get_int("test3d_running")
@@ -106,7 +107,7 @@ minetest.register_node("test3d:t21", {
  digiline = {
   receptor = {},
   effector = {
-   action = t21_digiline_receive
+   action = t400_digiline_receive
   }
  },
  on_receive_fields = function(pos,_,fields,sender)
@@ -143,13 +144,13 @@ minetest.register_node("test3d:t21", {
   sProgram = sProgram:sub(1,-1)
   meta:set_string("program",sProgram)
   print("Program:\n"..sProgram)
-  meta:set_int("pc",1)
+  meta:set_int("pc",0)
  end
 })
-print("T21 node registered")
+print("T400 node registered")
 
 minetest.register_abm({
- nodenames={"test3d:t21"},
+ nodenames={"test3d:t400"},
  interval=1,
  chance=1,
  action = function(pos)
@@ -167,17 +168,17 @@ minetest.register_abm({
     local pc = meta:get_int("pc")
     local acc = meta:get_int("acc")
     local bak = meta:get_int("bak")
-    print("Running T21 node with instance at position "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z).." (PC: "..tostring(pc)..", ACC: "..tostring(acc)..", BAK: "..tostring(bak)..")")
+    print("Running T400 node with instance at position "..tostring(pos.x)..","..tostring(pos.y)..","..tostring(pos.z).." (PC: "..tostring(pc)..", ACC: "..tostring(acc)..", BAK: "..tostring(bak)..")")
     local tProgram = string.split(meta:get_string("program"),"\n")
     local tLine = string.split(tProgram[pc]:upper())
     if pc == #tProgram then pc = 0 end
     meta:set_int("pc",pc+1)
    end
   end
-  t21_set_infotext(pos)
+  t400_set_infotext(pos)
  end,
 })
-print("T21 ABMs registered")
+print("T400 ABMs registered")
 
 --[[
 minetest.register_chatcommand("lua", { -- I'm a terrible person