diff --git a/README.md b/README.md
index 1e54b1a..5abc4b9 100644
--- a/README.md
+++ b/README.md
@@ -19,12 +19,13 @@ awesome features and is pretty advanced. Check it out. You can install both plug
 
 Big kudos to Yann -- a few features were _inspired_ by his code.
 
-My plugin, on the other hand, is still pretty basic and is the result of about a week's effort. I released a really early first version it because I think
+My plugin, on the other hand, is still pretty basic and is the result of about two weeks of work. I released a really early first version it because I think
 it's "good enough" to get started, and I can return to demo coding with its current state.
 
 ## Features
 
 - Parser / Lexer for MC68000 (yes, only 68000 right now!) assembly language files in VAsm / DevPac style
+- Inspection for validating the syntax the 68000 ISA.
 - Syntax highlighting and Color Settings Page (you should really modify the color settings to your likings!)
 - Mnemonics code completion
 - Symbols / Labels / Macros code completion
@@ -33,6 +34,7 @@ it's "good enough" to get started, and I can return to demo coding with its curr
 - Quote handler
 - Goto Symbol support
 - Structure view
+- Documentation provider for symbol definitions and mnemonics (listing available addressing modes etc.).
 
 ## Known issues
 
@@ -42,7 +44,6 @@ it's "good enough" to get started, and I can return to demo coding with its curr
 - No support for register replacement (e.g. registers replaced by `EQUR` or `EQURL` will cause syntax errors)
 - While the Lexer supports the -spaces option (where a space introduces a comment), this cannot be configured yet (default is off).
 - No support for other processor instructions, FPU or 68020+ address modes.
-- For versions < V0.4: No semantic checking for allowed address modes or data widths yet.
 - Unit Test coverage is not as good as it could be (ahem).
 - Missing but planned features:
     - Macro evaluation on invocation
@@ -70,11 +71,14 @@ make it work with JUnit 5. Feel free to use the code (in package ```de.platon42.
 
 ### V0.4 (unreleased)
 
+- Notice: Due to major new API use, this plugin no longer works on IDEs >=2019.3.1, but rather requires >=2020.3.
 - Enhancement: Added Structure View filters.
 - New: Added inspection to validate the correctness of a MC68000 instruction regarding operation size and address modes.
 - Bugfix: Added several missing assembler directives (`opt`, `machine`, etc.).
 - Bugfix: Uppercase hexadecimal literals were not parsed (JFlex bug?).
 - Bugfix: Interpretation of register lists was wrong in BNF.
+- New: Added Documentation Provider for symbol definitions (shows assigned declaration).
+- New: Added Documentation Provider for mnemonics (simple version, generated out of ISA information).
 
 ### V0.3 (28-Jul-21)
 
diff --git a/build.gradle b/build.gradle
index a047980..417b648 100644
--- a/build.gradle
+++ b/build.gradle
@@ -48,10 +48,7 @@ intellij {
 }
 
 runPluginVerifier {
-    ideVersions = ["IC-193.5662.53", "IC-212.4746.92", // 2019.3.1 - 2021.2
-                   "CL-193.5233.103", "CL-193.7288.25", // 2019.3
-                   "CL-201.6668.126", "CL-201.8743.17", // 2020.1
-                   "CL-202.6397.106", "CL-202.8194.17", // 2020.2
+    ideVersions = ["IC-203.6682.168", "IC-212.4746.92", // 2020.3 - 2021.2
                    "CL-203.5981.166", "CL-203.8084.11", // 2020.3
                    "CL-211.6693.114", "CL-211.7628.27", // 2021.1
                    "CL-212.4746.93"] // 2021.2
@@ -62,11 +59,14 @@ patchPluginXml {
     setChangeNotes("""
   <h4>V0.4 (unreleased)</h4>
     <ul>
+      <li>Notice: Due to major new API use, this plugin no longer works on IDEs >=2019.3.1, but rather requires >=2020.3.
       <li>Enhancement: Added Structure View filters.
       <li>New: Added inspection to validate the correctness of a MC68000 instruction regarding operation size and address modes.
       <li>Bugfix: Added several missing assembler directives (opt, machine, etc.).
       <li>Bugfix: Uppercase hexadecimal literals were not parsed (JFlex bug?).
       <li>Bugfix: Interpretation of register lists was wrong in BNF.
+      <li>New: Added Documentation Provider for symbol definitions (shows assigned declaration).
+      <li>New: Added Documentation Provider for mnemonics (simple version, generated out of ISA information).
     </ul>
   <h4>V0.3 (28-Jul-21)</h4>
     <ul>
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/asm/M68kIsa.kt b/src/main/java/de/platon42/intellij/plugins/m68k/asm/M68kIsa.kt
index 5787739..44e4302 100644
--- a/src/main/java/de/platon42/intellij/plugins/m68k/asm/M68kIsa.kt
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/asm/M68kIsa.kt
@@ -34,20 +34,20 @@ enum class Register(val regname: String, val num: Int) {
     }
 }
 
-enum class AddressMode {
-    IMMEDIATE_DATA,
-    ADDRESS_REGISTER_INDIRECT_PRE_DEC,
-    ADDRESS_REGISTER_INDIRECT_POST_INC,
-    ADDRESS_REGISTER_INDIRECT,
-    ADDRESS_REGISTER_INDIRECT_WITH_DISPLACEMENT,
-    PROGRAM_COUNTER_INDIRECT_WITH_DISPLACEMENT,
-    ADDRESS_REGISTER_INDIRECT_WITH_INDEX,
-    PROGRAM_COUNTER_INDIRECT_WITH_INDEX,
-    SPECIAL_REGISTER_DIRECT,
-    DATA_REGISTER_DIRECT,
-    ADDRESS_REGISTER_DIRECT,
-    REGISTER_LIST,
-    ABSOLUTE_ADDRESS
+enum class AddressMode(val description: String, val syntax: String) {
+    DATA_REGISTER_DIRECT("data register direct", "Dn"),
+    ADDRESS_REGISTER_DIRECT("address register direct", "An"),
+    ADDRESS_REGISTER_INDIRECT("address register indirect", "(An)"),
+    ADDRESS_REGISTER_INDIRECT_POST_INC("address register indirect with postincrement", "(An)+"),
+    ADDRESS_REGISTER_INDIRECT_PRE_DEC("address register indirect with predecrement", "-(An)"),
+    ADDRESS_REGISTER_INDIRECT_WITH_DISPLACEMENT("address register indirect with displacement", "(d16,An)"),
+    PROGRAM_COUNTER_INDIRECT_WITH_DISPLACEMENT("program counter indirect with displacement", "(d16,PC)"),
+    ADDRESS_REGISTER_INDIRECT_WITH_INDEX("address register indirect with index", "(d8,An,Xn)"),
+    PROGRAM_COUNTER_INDIRECT_WITH_INDEX("program counter indirect with index", "(d8,PC,Xn)"),
+    SPECIAL_REGISTER_DIRECT("special register", "ccr|usp|vbr"),
+    REGISTER_LIST("register list", "list"),
+    IMMEDIATE_DATA("immediate", "#<xxx>"),
+    ABSOLUTE_ADDRESS("absolute short/long", "(xxx).w|l")
 }
 
 const val OP_UNSIZED = 0
@@ -731,7 +731,7 @@ object M68kIsa {
             }
             .toSet()
 
-    fun findMatchingInstruction(mnemonic: String): List<IsaData> {
+    fun findMatchingInstructions(mnemonic: String): List<IsaData> {
         val lowerMnemonic = mnemonic.lowercase()
         return isaData
             .filter {
@@ -755,6 +755,13 @@ object M68kIsa {
         }
     }
 
+    fun findMatchingAddressMode(modes: List<AllowedAdrMode>, op1: AddressMode?, op2: AddressMode?, opSize: Int?, specialReg: String?): List<AllowedAdrMode> {
+        return modes.filter { am ->
+            isAddressModeMatching(am, op1, op2, specialReg)
+                    && ((opSize == null) || ((opSize and am.size) == opSize))
+        }
+    }
+
     fun findMatchingOpModeIgnoringSize(candidates: List<IsaData>, op1: AddressMode?, op2: AddressMode?, specialReg: String?): List<IsaData> {
         return candidates.filter {
             it.modes.any { am -> isAddressModeMatching(am, op1, op2, specialReg) }
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProvider.kt b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProvider.kt
new file mode 100644
index 0000000..be57905
--- /dev/null
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProvider.kt
@@ -0,0 +1,102 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.lang.documentation.AbstractDocumentationProvider
+import com.intellij.lang.documentation.DocumentationMarkup
+import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.util.text.HtmlBuilder
+import com.intellij.openapi.util.text.HtmlChunk
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiFile
+import de.platon42.intellij.plugins.m68k.asm.AddressMode
+import de.platon42.intellij.plugins.m68k.asm.IsaData
+import de.platon42.intellij.plugins.m68k.asm.M68kIsa
+import de.platon42.intellij.plugins.m68k.psi.M68kAsmInstruction
+import de.platon42.intellij.plugins.m68k.psi.M68kAsmOp
+import de.platon42.intellij.plugins.m68k.psi.M68kOperandSize
+import de.platon42.intellij.plugins.m68k.utils.M68kIsaUtil.findExactIsaDataForInstruction
+import de.platon42.intellij.plugins.m68k.utils.M68kIsaUtil.findOpSizeDescriptions
+
+class M68kInstructionDocumentationProvider : AbstractDocumentationProvider() {
+
+    override fun generateDoc(element: PsiElement, originalElement: PsiElement?): String? {
+        if (element is M68kAsmInstruction) {
+            val builder = HtmlBuilder()
+            val isaData = findExactIsaDataForInstruction(element)
+            if (isaData == null) {
+                M68kIsa.findMatchingInstructions(element.asmOp.mnemonic).forEach { buildDocForIsaData(it, builder) }
+            } else {
+                buildDocForIsaData(isaData, builder)
+            }
+            return builder.toString()
+        }
+        return null
+    }
+
+    private fun buildDocForIsaData(isaData: IsaData, builder: HtmlBuilder) {
+        val defBuilder = createDefinition(isaData)
+        builder.append(defBuilder.wrapWith(DocumentationMarkup.DEFINITION_ELEMENT))
+
+        val bindingRows = HtmlBuilder()
+        val headerCells = listOf(
+            HtmlChunk.text("Mnemonic").wrapWith(DocumentationMarkup.SECTION_HEADER_CELL),
+            HtmlChunk.text("Op1").wrapWith(DocumentationMarkup.SECTION_HEADER_CELL),
+            HtmlChunk.text("Op2").wrapWith(DocumentationMarkup.SECTION_HEADER_CELL)
+        )
+        bindingRows.append(HtmlChunk.tag("tr").children(headerCells))
+        isaData.modes.forEach { allowedAdrMode ->
+            val mnemonics = findOpSizeDescriptions(allowedAdrMode.size)
+                .map { HtmlChunk.text(isaData.mnemonic + it).wrapWith(HtmlChunk.p()) }
+            bindingRows.append(
+                HtmlChunk.tag("tr").children(
+                    DocumentationMarkup.SECTION_CONTENT_CELL.children(mnemonics),
+                    DocumentationMarkup.SECTION_CONTENT_CELL.child(collectAddressModes(allowedAdrMode.op1)),
+                    DocumentationMarkup.SECTION_CONTENT_CELL.child(collectAddressModes(allowedAdrMode.op2))
+                )
+            )
+        }
+
+        val contentBuilder = HtmlBuilder()
+        contentBuilder.append(bindingRows.br().wrapWith(DocumentationMarkup.SECTIONS_TABLE))
+
+        builder.append(contentBuilder.wrapWith(DocumentationMarkup.CONTENT_ELEMENT))
+    }
+
+    override fun generateHoverDoc(element: PsiElement, originalElement: PsiElement?): String? {
+        if (element is M68kAsmInstruction) {
+            val isaData = findExactIsaDataForInstruction(element) ?: return null
+            val defBuilder = createDefinition(isaData)
+
+            val builder = HtmlBuilder()
+            builder.append(defBuilder.wrapWith(DocumentationMarkup.DEFINITION_ELEMENT))
+            return builder.toString()
+        }
+        return null
+    }
+
+    private fun createDefinition(isaData: IsaData): HtmlBuilder {
+        val defBuilder = HtmlBuilder()
+        defBuilder.append(HtmlChunk.text(isaData.description).bold().wrapWith("pre"))
+        if (isaData.isPrivileged) {
+            defBuilder.append(HtmlChunk.font("red").addText("(privileged)").wrapWith("p"))
+        }
+        return defBuilder
+    }
+
+    private fun collectAddressModes(addressModes: Set<AddressMode>?): HtmlChunk {
+        if (addressModes == null) return HtmlChunk.text("")
+        val modes = HtmlBuilder()
+        addressModes.sortedBy(AddressMode::ordinal)
+            .forEach { modes.append(HtmlChunk.text(it.syntax).wrapWith(HtmlChunk.p())) }
+        return modes.toFragment()
+    }
+
+    override fun getCustomDocumentationElement(editor: Editor, file: PsiFile, contextElement: PsiElement?, targetOffset: Int): PsiElement? {
+        if (contextElement == null) return null
+        if (contextElement is M68kAsmInstruction) return contextElement
+        val parent = contextElement.parent ?: return null
+        if (parent is M68kAsmInstruction) return parent
+        if (parent is M68kAsmOp) return parent.parent
+        if (parent is M68kOperandSize) return parent.parent.parent
+        return null
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProvider.kt b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProvider.kt
new file mode 100644
index 0000000..62a4773
--- /dev/null
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProvider.kt
@@ -0,0 +1,39 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.lang.documentation.AbstractDocumentationProvider
+import com.intellij.openapi.editor.Editor
+import com.intellij.psi.PsiElement
+import com.intellij.psi.PsiFile
+import com.intellij.psi.util.PsiTreeUtil
+import de.platon42.intellij.plugins.m68k.asm.RWM_OP1_SHIFT
+import de.platon42.intellij.plugins.m68k.asm.RWM_OP2_SHIFT
+import de.platon42.intellij.plugins.m68k.asm.Register.Companion.getRegFromName
+import de.platon42.intellij.plugins.m68k.psi.M68kAddressRegister
+import de.platon42.intellij.plugins.m68k.psi.M68kAddressingMode
+import de.platon42.intellij.plugins.m68k.psi.M68kAsmInstruction
+import de.platon42.intellij.plugins.m68k.psi.M68kDataRegister
+import de.platon42.intellij.plugins.m68k.utils.M68kIsaUtil.findExactIsaDataAndAllowedAdrModeForInstruction
+
+class M68kRegisterFlowDocumentationProvider : AbstractDocumentationProvider() {
+    override fun generateDoc(element: PsiElement, originalElement: PsiElement?): String? {
+        if (element is M68kDataRegister || element is M68kAddressRegister) {
+            val register = getRegFromName(element.text)
+            val addressingMode = PsiTreeUtil.getParentOfType(element, M68kAddressingMode::class.java) ?: return null
+            val asmInstruction = PsiTreeUtil.getParentOfType(addressingMode, M68kAsmInstruction::class.java) ?: return null
+            val (isaData, adrMode) = findExactIsaDataAndAllowedAdrModeForInstruction(asmInstruction) ?: return "unknown instruction"
+
+            val opShift = if (asmInstruction.addressingModeList[0] == addressingMode) RWM_OP1_SHIFT else RWM_OP2_SHIFT
+
+            return register.regname
+        }
+        return null
+    }
+
+    override fun getCustomDocumentationElement(editor: Editor, file: PsiFile, contextElement: PsiElement?, targetOffset: Int): PsiElement? {
+        if (contextElement == null) return null
+        if (contextElement is M68kDataRegister || contextElement is M68kAddressRegister) return contextElement
+        val parent = contextElement.parent ?: return null
+        if (parent is M68kDataRegister || parent is M68kAddressRegister) return parent
+        return null
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProvider.kt b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProvider.kt
new file mode 100644
index 0000000..e03df8b
--- /dev/null
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProvider.kt
@@ -0,0 +1,24 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.lang.documentation.AbstractDocumentationProvider
+import com.intellij.lang.documentation.DocumentationMarkup
+import com.intellij.openapi.util.text.StringUtil
+import com.intellij.psi.PsiElement
+import de.platon42.intellij.plugins.m68k.psi.M68kAssignment
+import de.platon42.intellij.plugins.m68k.psi.M68kSymbolDefinition
+
+class M68kSymbolDefinitionDocumentationProvider : AbstractDocumentationProvider() {
+
+    override fun getQuickNavigateInfo(element: PsiElement, originalElement: PsiElement?): String? {
+        return generateDoc(element, originalElement)
+    }
+
+    override fun generateDoc(element: PsiElement, originalElement: PsiElement?): String? {
+        return if (element is M68kSymbolDefinition) {
+            // TODO find out how we can generate inner links for more symbol references inside the expression (DocumentationManagerUtil)
+            val value = (element.getParent() as M68kAssignment).expr.text
+            DocumentationMarkup.DEFINITION_START + StringUtil.escapeXmlEntities(element.name!!) + DocumentationMarkup.DEFINITION_END +
+                    DocumentationMarkup.CONTENT_START + StringUtil.escapeXmlEntities(value) + DocumentationMarkup.CONTENT_END
+        } else null
+    }
+}
\ No newline at end of file
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kSyntaxInspection.kt b/src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kSyntaxInspection.kt
index 7e72f8b..f905445 100644
--- a/src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kSyntaxInspection.kt
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/inspections/M68kSyntaxInspection.kt
@@ -5,7 +5,7 @@ import com.intellij.codeInspection.LocalQuickFix
 import com.intellij.codeInspection.ProblemDescriptor
 import com.intellij.codeInspection.ProblemHighlightType
 import de.platon42.intellij.plugins.m68k.asm.*
-import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findMatchingInstruction
+import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findMatchingInstructions
 import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findMatchingOpMode
 import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findMatchingOpModeIgnoringSize
 import de.platon42.intellij.plugins.m68k.asm.M68kIsa.findSupportedOpSizes
@@ -38,7 +38,7 @@ class M68kSyntaxInspection : AbstractBaseM68kLocalInspectionTool() {
     override fun checkAsmInstruction(asmInstruction: M68kAsmInstruction, manager: InspectionManager, isOnTheFly: Boolean): Array<ProblemDescriptor>? {
         val asmOp = asmInstruction.asmOp
         val mnemonicWithSize = asmOp.text
-        val isaData = findMatchingInstruction(asmOp.mnemonic)
+        val isaData = findMatchingInstructions(asmOp.mnemonic)
         if (isaData.isEmpty()) {
             return arrayOf(
                 manager.createProblemDescriptor(
@@ -61,16 +61,19 @@ class M68kSyntaxInspection : AbstractBaseM68kLocalInspectionTool() {
                 )
             )
         }
-        val op1 = getAddressModeForType(asmInstruction.addressingModeList.getOrNull(0))
-        val op2 = getAddressModeForType(asmInstruction.addressingModeList.getOrNull(1))
-        val specialReg1 = (asmInstruction.addressingModeList.getOrNull(0) as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
-        val specialReg2 = (asmInstruction.addressingModeList.getOrNull(1) as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
+        val amOp1 = asmInstruction.addressingModeList.getOrNull(0)
+        val amOp2 = asmInstruction.addressingModeList.getOrNull(1)
+        val op1 = getAddressModeForType(amOp1)
+        val op2 = getAddressModeForType(amOp2)
+        val specialReg1 = (amOp1 as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
+        val specialReg2 = (amOp2 as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
+        val specialReg = specialReg1 ?: specialReg2
         val opSize = asmOp.opSize
-        val matchingModeIsaData = findMatchingOpMode(isaData, op1, op2, opSize, specialReg1 ?: specialReg2)
+        val matchingModeIsaData = findMatchingOpMode(isaData, op1, op2, opSize, specialReg)
         if (matchingModeIsaData.isEmpty()) {
-            val matchingModeIsaDataIgnoringSize = findMatchingOpModeIgnoringSize(isaData, op1, op2, specialReg1 ?: specialReg2)
+            val matchingModeIsaDataIgnoringSize = findMatchingOpModeIgnoringSize(isaData, op1, op2, specialReg)
             if (matchingModeIsaDataIgnoringSize.isEmpty()) {
-                val matchingModeIsaDataSwapped = findMatchingOpModeIgnoringSize(isaData, op2, op1, specialReg1 ?: specialReg2)
+                val matchingModeIsaDataSwapped = findMatchingOpModeIgnoringSize(isaData, op2, op1, specialReg)
                 val supportedModesOp1 = isaData.flatMap { it.modes.flatMap { am -> am.op1 ?: emptySet() } }.toSet()
                 val supportedModesOp2 = isaData.flatMap { it.modes.flatMap { am -> am.op2 ?: emptySet() } }.toSet()
 
@@ -133,7 +136,7 @@ class M68kSyntaxInspection : AbstractBaseM68kLocalInspectionTool() {
             }
 
 
-            val supportedOpSizes = findSupportedOpSizes(matchingModeIsaDataIgnoringSize, op1, op2, specialReg1 ?: specialReg2)
+            val supportedOpSizes = findSupportedOpSizes(matchingModeIsaDataIgnoringSize, op1, op2, specialReg)
             return arrayOf(
                 when (supportedOpSizes) {
                     OP_UNSIZED ->
diff --git a/src/main/java/de/platon42/intellij/plugins/m68k/utils/M68kIsaUtil.kt b/src/main/java/de/platon42/intellij/plugins/m68k/utils/M68kIsaUtil.kt
new file mode 100644
index 0000000..dce2fc9
--- /dev/null
+++ b/src/main/java/de/platon42/intellij/plugins/m68k/utils/M68kIsaUtil.kt
@@ -0,0 +1,64 @@
+package de.platon42.intellij.plugins.m68k.utils
+
+import de.platon42.intellij.plugins.m68k.asm.*
+import de.platon42.intellij.plugins.m68k.psi.M68kAddressModeUtil
+import de.platon42.intellij.plugins.m68k.psi.M68kAsmInstruction
+import de.platon42.intellij.plugins.m68k.psi.M68kSpecialRegisterDirectAddressingMode
+
+object M68kIsaUtil {
+
+    // TODO if more than one result, do a check and consolidate
+    fun findExactIsaDataForInstruction(asmInstruction: M68kAsmInstruction): IsaData? =
+        findIsaDataForInstruction(asmInstruction).firstOrNull()?.first
+
+    // TODO if more than one result, do a check and consolidate
+    fun findExactIsaDataAndAllowedAdrModeForInstruction(asmInstruction: M68kAsmInstruction): Pair<IsaData, AllowedAdrMode>? {
+        val (isaData, adrModeList) = findIsaDataForInstruction(asmInstruction).firstOrNull() ?: return null
+        return isaData to adrModeList.first()
+    }
+
+    fun findIsaDataForInstruction(asmInstruction: M68kAsmInstruction): List<Pair<IsaData, List<AllowedAdrMode>>> {
+        val isaDataCandidates = M68kIsa.findMatchingInstructions(asmInstruction.asmOp.mnemonic)
+        if (isaDataCandidates.isEmpty()) return emptyList()
+
+        val amOp1 = asmInstruction.addressingModeList.getOrNull(0)
+        val amOp2 = asmInstruction.addressingModeList.getOrNull(1)
+        val op1 = M68kAddressModeUtil.getAddressModeForType(amOp1)
+        val op2 = M68kAddressModeUtil.getAddressModeForType(amOp2)
+        val specialReg1 = (amOp1 as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
+        val specialReg2 = (amOp2 as? M68kSpecialRegisterDirectAddressingMode)?.specialRegister?.text
+        val specialReg = specialReg1 ?: specialReg2
+        val opSize = asmInstruction.asmOp.opSize
+        val matchedIsaData =
+            M68kIsa.findMatchingOpMode(isaDataCandidates, op1, op2, opSize, specialReg)
+        return matchedIsaData.map { it to M68kIsa.findMatchingAddressMode(it.modes, op1, op2, opSize, specialReg) }
+    }
+
+    fun findOpSizeDescription(opSize: Int): String {
+        return when (opSize) {
+            OP_UNSIZED -> ""
+            OP_SIZE_B -> ".b"
+            OP_SIZE_W -> ".w"
+            OP_SIZE_L -> ".l"
+            OP_SIZE_S -> ".s"
+            OP_SIZE_BWL -> ".b|.w|.l"
+            OP_SIZE_WL -> ".w|.l"
+            OP_SIZE_SBW -> ".s|.b|.w"
+            else -> "?"
+        }
+    }
+
+    fun findOpSizeDescriptions(opSize: Int): Set<String> {
+        return when (opSize) {
+            OP_UNSIZED -> setOf("")
+            OP_SIZE_B -> setOf(".b")
+            OP_SIZE_W -> setOf(".w")
+            OP_SIZE_L -> setOf(".l")
+            OP_SIZE_S -> setOf(".s")
+            OP_SIZE_BWL -> setOf(".b", ".w", ".l")
+            OP_SIZE_WL -> setOf(".w", ".l")
+            OP_SIZE_SBW -> setOf(".s", ".b", ".w")
+            else -> setOf("?")
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/main/resources/META-INF/plugin.xml b/src/main/resources/META-INF/plugin.xml
index d743475..71c2579 100644
--- a/src/main/resources/META-INF/plugin.xml
+++ b/src/main/resources/META-INF/plugin.xml
@@ -10,7 +10,7 @@
     <p>
     <a href="https://github.com/chrisly42/mc68000-asm-plugin/blob/main/README.md">Full documentation here...</a>
     ]]></description>
-    <idea-version since-build="193.5233.103"/>
+    <idea-version since-build="203.5981.166"/>
 
     <depends>com.intellij.modules.lang</depends>
 
@@ -33,6 +33,12 @@
                                  implementationClass="de.platon42.intellij.plugins.m68k.refs.M68kSymbolReferenceElementManipulator"/>
         <lang.elementManipulator forClass="de.platon42.intellij.plugins.m68k.psi.M68kMacroCall"
                                  implementationClass="de.platon42.intellij.plugins.m68k.refs.M68kMacroCallElementManipulator"/>
+        <lang.documentationProvider language="MC68000"
+                                    implementationClass="de.platon42.intellij.plugins.m68k.documentation.M68kSymbolDefinitionDocumentationProvider"/>
+        <lang.documentationProvider language="MC68000"
+                                    implementationClass="de.platon42.intellij.plugins.m68k.documentation.M68kRegisterFlowDocumentationProvider"/>
+        <lang.documentationProvider language="MC68000"
+                                    implementationClass="de.platon42.intellij.plugins.m68k.documentation.M68kInstructionDocumentationProvider"/>
         <stubElementTypeHolder class="de.platon42.intellij.plugins.m68k.stubs.M68kElementTypes"/>
         <stubIndex implementation="de.platon42.intellij.plugins.m68k.stubs.M68kGlobalLabelStubIndex"/>
         <stubIndex implementation="de.platon42.intellij.plugins.m68k.stubs.M68kSymbolDefinitionStubIndex"/>
@@ -42,6 +48,7 @@
         <renameInputValidator implementation="de.platon42.intellij.plugins.m68k.psi.M68kRenameInputValidator"/>
 
         <localInspection implementationClass="de.platon42.intellij.plugins.m68k.inspections.M68kSyntaxInspection"
+                         displayName="Assembly instruction validity" groupName="M68k"
                          enabledByDefault="true" level="ERROR"/>
     </extensions>
 
diff --git a/src/test/java/de/platon42/intellij/plugins/m68k/documentation/AbstractDocumentationProviderTest.kt b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/AbstractDocumentationProviderTest.kt
new file mode 100644
index 0000000..ce402d8
--- /dev/null
+++ b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/AbstractDocumentationProviderTest.kt
@@ -0,0 +1,20 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.codeInsight.documentation.DocumentationManager
+import com.intellij.testFramework.fixtures.CodeInsightTestFixture
+import de.platon42.intellij.jupiter.LightCodeInsightExtension
+import de.platon42.intellij.jupiter.TestDataPath
+import de.platon42.intellij.plugins.m68k.AbstractM68kTest
+import org.junit.jupiter.api.extension.ExtendWith
+
+@ExtendWith(LightCodeInsightExtension::class)
+@TestDataPath("src/test/resources/documentation")
+abstract class AbstractDocumentationProviderTest : AbstractM68kTest() {
+
+    fun generateDocumentation(myFixture: CodeInsightTestFixture): String? {
+        val docElement = DocumentationManager.getInstance(myFixture.project).findTargetElement(myFixture.editor, myFixture.file)
+        val provider = DocumentationManager.getProviderFromElement(docElement)
+
+        return provider.generateDoc(docElement, myFixture.file.findElementAt(myFixture.caretOffset))
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProviderTest.kt b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProviderTest.kt
new file mode 100644
index 0000000..23862f0
--- /dev/null
+++ b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kInstructionDocumentationProviderTest.kt
@@ -0,0 +1,59 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.testFramework.fixtures.CodeInsightTestFixture
+import de.platon42.intellij.jupiter.LightCodeInsightExtension
+import de.platon42.intellij.jupiter.MyFixture
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+
+@ExtendWith(LightCodeInsightExtension::class)
+internal class M68kInstructionDocumentationProviderTest : AbstractDocumentationProviderTest() {
+
+    @Test
+    internal fun check_documentation_inside_mnemonic(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+ mo<caret>veq.l #40,d0
+        """
+        )
+        assertThat(generateDocumentation(myFixture)).isEqualTo(
+            """<div class="definition"><pre><b>Move Quick</b></pre></div><div class="content"><table class="sections"><tr><td class="section" valign="top">Mnemonic</td><td class="section" valign="top">Op1</td><td class="section" valign="top">Op2</td></tr><tr><td valign="top"><p>moveq.l</p></td><td valign="top"><p>#&lt;xxx&gt;</p></td><td valign="top"><p>Dn</p></td></tr><br/></table></div>"""
+        )
+    }
+
+    @Test
+    internal fun check_documentation_inside_op_size(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+ bra.<caret>s label
+        """
+        )
+        assertThat(generateDocumentation(myFixture)).isEqualTo(
+            """<div class="definition"><pre><b>Branch</b></pre></div><div class="content"><table class="sections"><tr><td class="section" valign="top">Mnemonic</td><td class="section" valign="top">Op1</td><td class="section" valign="top">Op2</td></tr><tr><td valign="top"><p>bra.s</p><p>bra.b</p><p>bra.w</p></td><td valign="top"><p>(xxx).w|l</p></td><td valign="top"></td></tr><br/></table></div>"""
+        )
+    }
+
+    @Test
+    internal fun check_documentation_for_privileged_instruction(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+ <caret>reset
+        """
+        )
+        assertThat(generateDocumentation(myFixture)).isEqualTo(
+            """<div class="definition"><pre><b>Reset External Devices</b></pre><p><font color="red">(privileged)</font></p></div><div class="content"><table class="sections"><tr><td class="section" valign="top">Mnemonic</td><td class="section" valign="top">Op1</td><td class="section" valign="top">Op2</td></tr><tr><td valign="top"><p>reset</p></td><td valign="top"></td><td valign="top"></td></tr><br/></table></div>"""
+        )
+    }
+
+    @Test
+    internal fun check_documentation_if_there_is_no_concrete_match(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+ <caret>cmp
+        """
+        )
+        assertThat(generateDocumentation(myFixture))
+            .contains("<b>Compare</b>", "<b>Compare Address</b>", "<b>Compare Immediate</b>", "<b>Compare Memory to Memory</b>")
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProviderTest.kt b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProviderTest.kt
new file mode 100644
index 0000000..7350677
--- /dev/null
+++ b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kRegisterFlowDocumentationProviderTest.kt
@@ -0,0 +1,31 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.testFramework.fixtures.CodeInsightTestFixture
+import de.platon42.intellij.jupiter.LightCodeInsightExtension
+import de.platon42.intellij.jupiter.MyFixture
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+
+@ExtendWith(LightCodeInsightExtension::class)
+internal class M68kRegisterFlowDocumentationProviderTest : AbstractDocumentationProviderTest() {
+
+    @Test
+    internal fun check_documentation_for_a_symbol_definition(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+label
+    moveq.l #0,d0
+    add.w   #1,d0
+    move.w  d0,d1
+    move.b  d2,d0
+    addq.b  #1,d0
+    move.w  d<caret>0,d1
+    move.l  d0,d2
+    move.w  d1,d2
+    rts
+        """
+        )
+        assertThat(generateDocumentation(myFixture)).isEqualTo("d0")
+    }
+}
\ No newline at end of file
diff --git a/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProviderTest.kt b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProviderTest.kt
new file mode 100644
index 0000000..2d4b3da
--- /dev/null
+++ b/src/test/java/de/platon42/intellij/plugins/m68k/documentation/M68kSymbolDefinitionDocumentationProviderTest.kt
@@ -0,0 +1,24 @@
+package de.platon42.intellij.plugins.m68k.documentation
+
+import com.intellij.testFramework.fixtures.CodeInsightTestFixture
+import de.platon42.intellij.jupiter.LightCodeInsightExtension
+import de.platon42.intellij.jupiter.MyFixture
+import org.assertj.core.api.Assertions.assertThat
+import org.junit.jupiter.api.Test
+import org.junit.jupiter.api.extension.ExtendWith
+
+@ExtendWith(LightCodeInsightExtension::class)
+internal class M68kSymbolDefinitionDocumentationProviderTest : AbstractDocumentationProviderTest() {
+
+    @Test
+    internal fun check_documentation_for_a_symbol_definition(@MyFixture myFixture: CodeInsightTestFixture) {
+        myFixture.configureByText(
+            "documentme.asm", """
+PIC_WIDTH = 320
+ move.w #PIC_WIDT<caret>H,d0
+        """
+        )
+        assertThat(generateDocumentation(myFixture))
+            .isEqualTo("<div class='definition'><pre>PIC_WIDTH</pre></div><div class='content'>320</div>")
+    }
+}
\ No newline at end of file