diff --git a/AGENTS.md b/AGENTS.md
index 8e6c0d9..94cd132 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -30,7 +30,8 @@ scl_lsp/
 │   ├── diagnostics.lua     # Linter
 │   ├── formatter.lua       # Document formatter
 │   ├── treesitter.lua      # Tree-sitter integration
-│   ├── plc_json.lua        # External UDT loading
+│   ├── plc_json.lua        # External UDT/DB loading
+│   ├── builtin_instructions.lua  # TIA Portal built-in types/FBs/functions
 │   └── json.lua            # JSON encoder/decoder
 ├── lua/scl/                 # Neovim plugin (uses require)
 │   ├── init.lua            # Main plugin setup
@@ -155,12 +156,30 @@ if ok and module then
 end
 ```
 
+## Diagnostics
+
+The LSP validates data types and provides warnings for unknown types. It recognizes:
+- **Elementary data types** - BOOL, BYTE, WORD, DWORD, LWORD, CHAR, WCHAR, STRING, WSTRING, INT, DINT, LINT, USINT, SINT, UINT, UDINT, ULINT, REAL, LREAL, TIME, DATE, TOD, TIME_OF_DAY, DATE_AND_TIME, DT, S5TIME, LTIME, DTL
+- **Timer/counter types** - IEC_TIMER, TON_TIME, TOF_TIME, TONR_TIME, TP_TIME, CTU, CTD, CTUD
+- **TIA Portal built-in instructions** - Functions and function blocks
+- **Workspace types** - UDTs from `.udt` files and data blocks from `.db` files
+
 ## Completion Triggers
 - `#` - Local variables (after BEGIN)
 - `.` - Member access (UDT/DB)
 - `"` - Global DB names
 - `(` - FB/Function parameters
 - ` ` (space) - General completion
+- `:` - Type declaration (in VAR section)
+
+### Completion Types
+The LSP provides auto-completion for:
+- **Local variables** - Variables declared in VAR sections
+- **UDT types** - User-defined types from `.udt` files
+- **Global DBs** - Data blocks from `.db` files  
+- **Elementary types** - BOOL, INT, DINT, REAL, TIME, etc.
+- **TIA Portal built-in FBs** - TON, TOF, TP, CTU, CTD, CTUD, R_TRIG, etc.
+- **TIA Portal built-in functions** - ADD, SUB, MUL, DIV, SIN, COS, SQRT, etc.
 
 ## Formatter Options
 
diff --git a/src/builtin_instructions.lua b/src/builtin_instructions.lua
new file mode 100644
index 0000000..17c90c1
--- /dev/null
+++ b/src/builtin_instructions.lua
@@ -0,0 +1,249 @@
+local M = {}
+
+M.FUNCTIONS = {
+  ADD = true,
+  SUB = true,
+  MUL = true,
+  DIV = true,
+  MOD = true,
+  ABS = true,
+  NEG = true,
+  SQR = true,
+  SQRT = true,
+  EXP = true,
+  LN = true,
+  LOG = true,
+  SIN = true,
+  COS = true,
+  TAN = true,
+  ASIN = true,
+  ACOS = true,
+  ATAN = true,
+  MIN = true,
+  MAX = true,
+  LIMIT = true,
+  CALCULATE = true,
+  CONVERT = true,
+  ROUND = true,
+  TRUNC = true,
+  CEIL = true,
+  FLOOR = true,
+  SCALE_X = true,
+  NORM_X = true,
+  LEN = true,
+  CONCAT = true,
+  LEFT = true,
+  RIGHT = true,
+  MID = true,
+  INSERT = true,
+  DELETE = true,
+  REPLACE = true,
+  FIND = true,
+  AND = true,
+  OR = true,
+  XOR = true,
+  NOT = true,
+  SHL = true,
+  SHR = true,
+  ROL = true,
+  ROR = true,
+  DECO = true,
+  ENCO = true,
+  BCD_I = true,
+  I_BCD = true,
+  DI_BCD = true,
+  DI_R = true,
+  I_DI = true,
+  R_DI = true,
+  R_DB = true,
+  MOVE = true,
+  FILL = true,
+  SWAP = true,
+  PEEK = true,
+  POKE = true,
+  GET_ERROR = true,
+  GET_ERR_ID = true,
+  RESET_ERR = true,
+  T_CONV = true,
+  T_ADD = true,
+  T_SUB = true,
+  T_DIFF = true,
+  T_COMBINE = true,
+  DT_DATE = true,
+  DT_TOD = true,
+  DATE_TO_DTL = true,
+  DTL_TO_DATE = true,
+  TOD_TO_DTL = true,
+  DTL_TO_TOD = true,
+  TimeToTicks = true,
+  TicksToTime = true,
+  GETHIGHNUM = true,
+  GETLOWNUM = true,
+  SAMPLE = true,
+  SAMPLE_TRIG = true,
+  WRIT_HIST = true,
+  READ_HIST = true,
+  COMPRESS = true,
+  READFILE = true,
+  WRITEFILE = true,
+  READ_DB = true,
+  WRITE_DB = true,
+  RDREC = true,
+  WRREC = true,
+  RALRM = true,
+  GET_DIAG = true,
+  DPRINT = true,
+  CTRL_PWM = true,
+  CTRL_PTO = true,
+  STATUS_PTO = true,
+  HOME = true,
+  MOVE_JOG = true,
+  MOVE_VEL = true,
+  MOVE_AXIS = true,
+  POS_PULSE = true,
+  POS_MC = true,
+  SET_CAM = true,
+  CAM_TB = true,
+  CAM_TE = true,
+  CAM_DOWN = true,
+  MC_CamIn = true,
+  MC_CamOut = true,
+  MC_Superimpose = true,
+  MC_GearIn = true,
+  MC_GearOut = true,
+  MC_Phasing = true,
+  MC_CombineAxes = true,
+  MC_Interpolate = true,
+  MC_MoveLinear = true,
+  MC_MoveCircular = true,
+  MC_MoveDirect = true,
+  MC_Home = true,
+  MC_Halt = true,
+  MC_Stop = true,
+  MC_Power = true,
+  MC_Reset = true,
+  MC_ReadParam = true,
+  MC_WriteParam = true,
+  MC_ReadAxisError = true,
+  MC_TouchProbe = true,
+  MC_AbortTrigger = true,
+  MC_ExtSetPointGen = true,
+  MC_Generator = true,
+  MC_BRIDGE = true,
+  MC_BRIDGE_OFF = true,
+  ENABLE = true,
+  DISABLE = true,
+  DISPLAY = true,
+  LOG_EVENT = true,
+  ALARM = true,
+  ALARM_DQ = true,
+  GET_ALARM = true,
+  GETINST = true,
+  GETALARMST = true,
+  CHANGEOVER = true,
+  REPLY_VALUE = true,
+  NOTIFY = true,
+  NOTIFY_WITH_ACK = true,
+  ASGEN = true,
+  HMI_R_DISCONNECT = true,
+  HMI_R_CONNECT = true,
+  HMI_R_SEND = true,
+  HMI_R_RECEIVE = true,
+  HMI_R_GET_STATE = true,
+  MODBUSPN = true,
+  MODBUSCP = true,
+  TSEND = true,
+  TRCV = true,
+  TCON = true,
+  TDISCON = true,
+  TSEND_C = true,
+  TRCV_C = true,
+  TUSEND = true,
+  TURCV = true,
+  TCONNECT = true,
+  TDISCONNECT = true,
+  GETHNSON = true,
+  DELHNSON = true,
+  DNS_CLIENT = true,
+  DHCP_CLIENT = true,
+  DCP_CLIENT = true,
+}
+
+M.FUNCTION_BLOCKS = {
+  TON = true,
+  TOF = true,
+  TP = true,
+  TONR = true,
+  CTU = true,
+  CTD = true,
+  CTUD = true,
+  IEC_TIMER = true,
+  IEC_TON = true,
+  IEC_TOF = true,
+  IEC_TP = true,
+  IEC_COUNTER = true,
+  IEC_CTU = true,
+  IEC_CTD = true,
+  IEC_CTUD = true,
+  R_TRIG = true,
+  F_TRIG = true,
+  SR = true,
+  RS = true,
+  SCHEDULE = true,
+  BPM = true,
+  LOG = true,
+  DATALOG = true,
+}
+
+M.DATA_TYPES = {
+  BOOL = true,
+  BYTE = true,
+  WORD = true,
+  DWORD = true,
+  LWORD = true,
+  CHAR = true,
+  WCHAR = true,
+  STRING = true,
+  WSTRING = true,
+  INT = true,
+  DINT = true,
+  LINT = true,
+  USINT = true,
+  SINT = true,
+  UINT = true,
+  UDINT = true,
+  ULINT = true,
+  REAL = true,
+  LREAL = true,
+  TIME = true,
+  DATE = true,
+  TOD = true,
+  TIME_OF_DAY = true,
+  DATE_AND_TIME = true,
+  DT = true,
+  S5TIME = true,
+  LTIME = true,
+  DTL = true,
+}
+
+function M.is_known_function(name)
+  return M.FUNCTIONS[name:upper()] or false
+end
+
+function M.is_known_function_block(name)
+  return M.FUNCTION_BLOCKS[name:upper()] or false
+end
+
+function M.is_known_data_type(name)
+  return M.DATA_TYPES[name:upper()] or false
+end
+
+function M.is_known_instruction(name)
+  return M.is_known_function(name) or M.is_known_function_block(name) or false
+end
+
+function M.is_known_type_or_instruction(name)
+  return M.is_known_data_type(name) or M.is_known_instruction(name) or false
+end
+
+return M
diff --git a/src/diagnostics.lua b/src/diagnostics.lua
index fb77765..f399a76 100644
--- a/src/diagnostics.lua
+++ b/src/diagnostics.lua
@@ -16,6 +16,7 @@ end
 package.path = package.path .. ";" .. script_path .. "/?.lua"
 
 local parser = dofile(script_path .. "/parser.lua")
+local builtin = dofile(script_path .. "/builtin_instructions.lua")
 
 local DiagnosticSeverity = {
   Error = 1,
@@ -156,9 +157,16 @@ function M.validate_diagnostics(content, workspace_types, root_dir)
              upper_type ~= "WSTRING" and upper_type ~= "TIME" and upper_type ~= "DATE" and
              upper_type ~= "TIME_OF_DAY" and upper_type ~= "DATE_AND_TIME" and
              upper_type ~= "S5TIME" and upper_type ~= "LTIME" and
+             upper_type ~= "USINT" and upper_type ~= "SINT" and upper_type ~= "UINT" and
+             upper_type ~= "UDINT" and upper_type ~= "LINT" and upper_type ~= "ULINT" and
+             upper_type ~= "TOD" and upper_type ~= "DTL" and
              upper_type ~= "IEC_TIMER" and upper_type ~= "TON_TIME" and
              upper_type ~= "TOF_TIME" and upper_type ~= "TONR_TIME" and
-             upper_type ~= "TP_TIME" then
+             upper_type ~= "TP_TIME" and upper_type ~= "IEC_TON" and
+             upper_type ~= "IEC_TOF" and upper_type ~= "IEC_TP" and
+             upper_type ~= "IEC_COUNTER" and upper_type ~= "CTU" and
+             upper_type ~= "CTD" and upper_type ~= "CTUD" and
+             not builtin.is_known_type_or_instruction(upper_type) then
             table.insert(diagnostics, {
               range = range_to_lsp(line_num, 0, line_num, #line),
               severity = DiagnosticSeverity.Warning,
diff --git a/src/main.lua b/src/main.lua
index 886f6f5..b76b7fa 100644
--- a/src/main.lua
+++ b/src/main.lua
@@ -26,6 +26,7 @@ local treesitter = dofile(script_path .. "/treesitter.lua")
 local plc_json = dofile(script_path .. "/plc_json.lua")
 local diagnostics = dofile(script_path .. "/diagnostics.lua")
 local formatter = dofile(script_path .. "/formatter.lua")
+local builtin = dofile(script_path .. "/builtin_instructions.lua")
 
 local documents = {}
 
@@ -57,7 +58,7 @@ local semanticTokenTypes = {
 local capabilities = {
 	hoverProvider = true,
 	completionProvider = {
-		triggerCharacters = { ".", "#", "(" },
+		triggerCharacters = { ".", "#", "(", " ", ":", ";", "\n" },
 		resolveProvider = false,
 	},
 	definitionProvider = true,
@@ -385,6 +386,27 @@ function handlers.textDocument_completion(params)
 		local line = lines[line_idx]
 		local col = params.position.character
 		local trigger = col > 0 and line:sub(col, col) or ""
+		local line_before = col > 1 and line:sub(1, col - 1) or ""
+
+		-- Get word prefix being typed (for filtering)
+		local prefix_start = col - 1
+		while prefix_start > 0 and line:sub(prefix_start, prefix_start):match("[%w_]") do
+			prefix_start = prefix_start - 1
+		end
+		local word_prefix = line:sub(prefix_start + 1, col - 1)
+
+		-- Check if we're in VAR section
+		local in_var_section = false
+		for i = line_idx - 1, 1, -1 do
+			local prev_line = lines[i]:gsub("^%s+", ""):gsub("%s+$", "")
+			if prev_line:match("^END_VAR") or prev_line:match("^VAR_TEMP") or prev_line:match("^VAR_IN_OUT") or prev_line:match("^VAR_OUTPUT") or prev_line:match("^VAR_INPUT") then
+				break
+			end
+			if prev_line:match("^VAR%s*$") or prev_line:match("^VAR$") then
+				in_var_section = true
+				break
+			end
+		end
 
 		if trigger == "#" then
 			if doc.variables then
@@ -450,6 +472,53 @@ function handlers.textDocument_completion(params)
 					})
 				end
 			end
+		else
+			-- Check context before cursor
+			local is_var_decl = line_before:match(":%s*$")
+
+			-- Helper to add item with prefix filtering
+			local function add_item(name, kind_val, detail_text)
+				if word_prefix == "" or name:upper():find("^" .. word_prefix:upper()) then
+					table.insert(items, {
+						label = name,
+						kind = kind_val,
+						detail = detail_text,
+						insertText = name,
+						insertTextFormat = 1,
+					})
+				end
+			end
+
+			if in_var_section or is_var_decl then
+				-- In VAR section: show data types and function blocks
+				for type_name, _ in pairs(builtin.DATA_TYPES) do
+					add_item(type_name, 7, "Data type")
+				end
+
+				for fb_name, _ in pairs(builtin.FUNCTION_BLOCKS) do
+					add_item(fb_name, 6, "Function block")
+				end
+
+				-- Also add workspace types if available
+				if doc.types then
+					for type_name, type_info in pairs(doc.types) do
+						add_item(type_name, 7, type_info.kind or "Type")
+					end
+				end
+			else
+				-- General context: show all
+				for type_name, _ in pairs(builtin.DATA_TYPES) do
+					add_item(type_name, 7, "Data type")
+				end
+
+				for fb_name, _ in pairs(builtin.FUNCTION_BLOCKS) do
+					add_item(fb_name, 6, "Function block")
+				end
+
+				for func_name, _ in pairs(builtin.FUNCTIONS) do
+					add_item(func_name, 3, "Function")
+				end
+			end
 		end
 	end
 
diff --git a/src/node-types.json b/src/node-types.json
index 22af526..1c13d24 100644
--- a/src/node-types.json
+++ b/src/node-types.json
@@ -1524,10 +1524,18 @@
     "type": "tod",
     "named": false
   },
+  {
+    "type": "TOD",
+    "named": false
+  },
   {
     "type": "uint",
     "named": false
   },
+  {
+    "type": "UInt",
+    "named": false
+  },
   {
     "type": "usint",
     "named": false
@@ -1552,4 +1560,4 @@
     "type": "}",
     "named": false
   }
-]
\ No newline at end of file
+]
diff --git a/src/plc_json.lua b/src/plc_json.lua
index e4833db..8a504c0 100644
--- a/src/plc_json.lua
+++ b/src/plc_json.lua
@@ -85,24 +85,33 @@ local function parse_scl_type_file(content)
   local current_type_name = nil
   local pending_type_name = nil
 
+  content = content:gsub("^([\239\187\191]+)", "")
+
   local lines = {}
   for line in content:gmatch("[^\n]+") do table.insert(lines, line) end
 
   for i, line in ipairs(lines) do
     local trimmed = line:gsub("^%s+", ""):gsub("%s+$", "")
 
-    if trimmed:match("^TYPE%s*:?%s*$") then
+    if trimmed:match("^TYPE%s") or trimmed:match('^TYPE"') or trimmed == "TYPE" then
       in_type = true
       in_struct = false
       current_type_name = nil
       pending_type_name = nil
+      local type_name = trimmed:match('TYPE%s+"([^"]+)"') or trimmed:match("^TYPE%s+(%w+)")
+      if type_name then
+        pending_type_name = type_name
+      end
+      in_struct = false
+      current_type_name = nil
+      pending_type_name = nil
     elseif trimmed:match("^END_TYPE") then
       in_type = false
       in_struct = false
       current_type_name = nil
       pending_type_name = nil
     elseif in_type then
-      if trimmed:match("^END_STRUCT") then
+      if trimmed:match("^END_STRUCT") or trimmed:match("^END_STRUCT;") then
         in_struct = false
         current_type_name = nil
         pending_type_name = nil
@@ -144,6 +153,48 @@ local function parse_scl_type_file(content)
   return types
 end
 
+local function parse_db_file(content)
+  local types = {}
+  local in_var = false
+  local current_type_name = nil
+
+  content = content:gsub("^([\239\187\191]+)", "")
+
+  local lines = {}
+  for line in content:gmatch("[^\n]+") do table.insert(lines, line) end
+
+  for i, line in ipairs(lines) do
+    local trimmed = line:gsub("^%s+", ""):gsub("%s+$", "")
+
+    if trimmed:match('^DATA_BLOCK%s+"([^"]+)"') then
+      current_type_name = trimmed:match('^DATA_BLOCK%s+"([^"]+)"')
+      types[current_type_name] = {
+        name = current_type_name,
+        kind = "struct",
+        fields = {},
+        source = "db_file",
+      }
+    elseif trimmed:match("^END_VAR") then
+      in_var = false
+    elseif trimmed:match("^VAR%s*$") or trimmed:match("^VAR ") then
+      in_var = true
+    elseif in_var and current_type_name and types[current_type_name] and trimmed ~= "" and not trimmed:match("^//") then
+      local field_name = line:match("^%s*(%w+)%s*:")
+      if field_name then
+        local field_type = line:match(":%s*([%w_]+)")
+        if field_type then
+          table.insert(types[current_type_name].fields, {
+            name = field_name,
+            type = field_type,
+          })
+        end
+      end
+    end
+  end
+
+  return types
+end
+
 function M.load_types_from_workspace(root_dir)
   local types = {}
 
@@ -213,6 +264,21 @@ function M.load_types_from_workspace(root_dir)
     end
   end
 
+  -- Also scan for .db files
+  local db_files = scan_files_recursive(root_dir, "*.db")
+  for _, filepath in ipairs(db_files) do
+    local content = run_command("cat " .. filepath:gsub(" ", "\\ "))
+    if content then
+      local db_types = parse_db_file(content)
+      for name, typ in pairs(db_types) do
+        typ.source = "db_file"
+        if not types[name] then
+          types[name] = typ
+        end
+      end
+    end
+  end
+
   return types
 end