diff --git a/codeAst/src/prog8/code/ast/AstStatements.kt b/codeAst/src/prog8/code/ast/AstStatements.kt
index 9f9a12d07..085c9aef1 100644
--- a/codeAst/src/prog8/code/ast/AstStatements.kt
+++ b/codeAst/src/prog8/code/ast/AstStatements.kt
@@ -8,7 +8,7 @@ class PtAsmSub(
     val address: UInt?,
     val clobbers: Set<CpuRegister>,
     val parameters: List<Pair<PtSubroutineParameter, RegisterOrStatusflag>>,
-    val returnTypes: List<DataType>,
+    val returnTypes: List<DataType>,    // TODO join with register as Pairs ?
     val retvalRegisters: List<RegisterOrStatusflag>,
     val inline: Boolean,
     position: Position
diff --git a/codeGenExperimental/src/prog8/codegen/experimental/CodeGen.kt b/codeGenExperimental/src/prog8/codegen/experimental/CodeGen.kt
index 7c0a320d4..9ebde884a 100644
--- a/codeGenExperimental/src/prog8/codegen/experimental/CodeGen.kt
+++ b/codeGenExperimental/src/prog8/codegen/experimental/CodeGen.kt
@@ -863,14 +863,14 @@ class CodeGen(internal val program: PtProgram,
     }
 
     private fun translate(block: PtBlock): IRBlock {
-        val vmblock = IRBlock(block.name, block.address, block.alignment, block.position)   // no use for other attributes yet?
+        val vmblock = IRBlock(block.name, block.address, translate(block.alignment), block.position)   // no use for other attributes yet?
         for (child in block.children) {
             when(child) {
                 is PtNop -> { /* nothing */ }
                 is PtAssignment -> { /* global variable initialization is done elsewhere */ }
                 is PtScopeVarsDecls -> { /* vars should be looked up via symbol table */ }
                 is PtSub -> {
-                    val vmsub = IRSubroutine(child.name, child.returntype, child.position)
+                    val vmsub = IRSubroutine(child.name, translate(child.parameters), child.returntype, child.position)
                     for (subchild in child.children) {
                         val translated = translateNode(subchild)
                         if(translated.isNotEmpty())
@@ -880,7 +880,11 @@ class CodeGen(internal val program: PtProgram,
                 }
                 is PtAsmSub -> {
                     val assembly = if(child.children.isEmpty()) "" else (child.children.single() as PtInlineAssembly).assembly
-                    vmblock += IRAsmSubroutine(child.name, child.position, child.address, assembly)
+                    vmblock += IRAsmSubroutine(child.name, child.position, child.address,
+                        child.clobbers,
+                        child.parameters.map { IRAsmSubroutine.IRAsmSubParam(it.first.name, it.first.type, it.second) },
+                        child.returnTypes.zip(child.retvalRegisters),
+                        assembly)
                 }
                 is PtInlineAssembly -> {
                     vmblock += IRInlineAsmChunk(child.assembly, child.position)
@@ -891,6 +895,20 @@ class CodeGen(internal val program: PtProgram,
         return vmblock
     }
 
+    private fun translate(parameters: List<PtSubroutineParameter>) =
+        parameters.map {
+            val flattenedName = (it.definingSub()!!.scopedName + it.name)
+            symbolTable.flat.getValue(flattenedName) as StStaticVariable
+        }
+
+    private fun translate(alignment: PtBlock.BlockAlignment): IRBlock.BlockAlignment {
+        return when(alignment) {
+            PtBlock.BlockAlignment.NONE -> IRBlock.BlockAlignment.NONE
+            PtBlock.BlockAlignment.WORD -> IRBlock.BlockAlignment.WORD
+            PtBlock.BlockAlignment.PAGE -> IRBlock.BlockAlignment.PAGE
+        }
+    }
+
 
     internal fun vmType(type: DataType): VmDataType {
         return when(type) {
diff --git a/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt b/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
index 9d6976b51..6e957fd4d 100644
--- a/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
+++ b/compiler/src/prog8/compiler/astprocessing/IntermediateAstMaker.kt
@@ -302,6 +302,8 @@ class IntermediateAstMaker(val program: Program) {
             srcSub.asmReturnvaluesRegisters,
             srcSub.inline,
             srcSub.position)
+        sub.parameters.forEach { it.first.parent=sub }
+
         if(srcSub.asmAddress==null) {
             var combinedAsm = ""
             for (asm in srcSub.statements)
@@ -322,6 +324,7 @@ class IntermediateAstMaker(val program: Program) {
             srcSub.returntypes.singleOrNull(),
             srcSub.inline,
             srcSub.position)
+        sub.parameters.forEach { it.parent=sub }
 
         if(vardecls.isNotEmpty()) sub.add(makeScopeVarsDecls(vardecls, sub.position))
         for (statement in statements)
diff --git a/examples/test.p8 b/examples/test.p8
index b8574fad7..ee1676e23 100644
--- a/examples/test.p8
+++ b/examples/test.p8
@@ -55,10 +55,10 @@ a_label:
 
         qq=global1
         qq=other.global2
-        nested()
+        nested(11,22)
         main.start.nested.nested2()
 
-        sub nested() {
+        sub nested(ubyte a1, ubyte a2) {
             qq++
             txt.print("zzz")
             nested2()
diff --git a/intermediate/src/prog8/intermediate/IRFileReader.kt b/intermediate/src/prog8/intermediate/IRFileReader.kt
index 3e93ed6b1..24c85a0ac 100644
--- a/intermediate/src/prog8/intermediate/IRFileReader.kt
+++ b/intermediate/src/prog8/intermediate/IRFileReader.kt
@@ -1,7 +1,6 @@
 package prog8.intermediate
 
 import prog8.code.*
-import prog8.code.ast.PtBlock
 import prog8.code.core.*
 import prog8.code.target.*
 import java.nio.file.Path
@@ -30,7 +29,7 @@ class IRFileReader(outputDir: Path, programName: String) {
         val memorymapped = parseMemMapped(lines)
         val slabs = parseSlabs(lines)
         val initGlobals = parseInitGlobals(lines)
-        val blocks = parseBlocksUntilProgramEnd(lines)
+        val blocks = parseBlocksUntilProgramEnd(lines, variables)
 
         val st = SymbolTable()
         variables.forEach { st.add(it) }
@@ -226,7 +225,7 @@ class IRFileReader(outputDir: Path, programName: String) {
         return chunk
     }
 
-    private fun parseBlocksUntilProgramEnd(lines: Iterator<String>): List<IRBlock> {
+    private fun parseBlocksUntilProgramEnd(lines: Iterator<String>, variables: List<StStaticVariable>): List<IRBlock> {
         val blocks = mutableListOf<IRBlock>()
         while(true) {
             var line = lines.next()
@@ -234,27 +233,27 @@ class IRFileReader(outputDir: Path, programName: String) {
                 line = lines.next()
             if (line == "</PROGRAM>")
                 break
-            blocks.add(parseBlock(line, lines))
+            blocks.add(parseBlock(line, lines, variables))
         }
         return blocks
     }
 
     private val blockPattern = Regex("<BLOCK NAME=(.+) ADDRESS=(.+) ALIGN=(.+) POS=(.+)>")
     private val inlineAsmPattern = Regex("<INLINEASM POS=(.+)>")
-    private val asmsubPattern = Regex("<ASMSUB NAME=(.+) ADDRESS=(.+) POS=(.+)>")
+    private val asmsubPattern = Regex("<ASMSUB NAME=(.+) ADDRESS=(.+) CLOBBERS=(.+) POS=(.+)>")
     private val subPattern = Regex("<SUB NAME=(.+) RETURNTYPE=(.+) POS=(.+)>")
     private val posPattern = Regex("\\[(.+): line (.+) col (.+)-(.+)\\]")
     private val instructionPattern = Regex("""([a-z]+)(\.b|\.w|\.f)?(.*)""", RegexOption.IGNORE_CASE)
     private val labelPattern = Regex("""_([a-zA-Z\d\._]+):""")
 
-    private fun parseBlock(startline: String, lines: Iterator<String>): IRBlock {
+    private fun parseBlock(startline: String, lines: Iterator<String>, variables: List<StStaticVariable>): IRBlock {
         var line = startline
         if(!line.startsWith("<BLOCK "))
             throw IRParseException("invalid BLOCK")
         val match = blockPattern.matchEntire(line) ?: throw IRParseException("invalid BLOCK")
         val (name, address, align, position) = match.destructured
         val addressNum = if(address=="null") null else address.toUInt()
-        val block = IRBlock(name, addressNum, PtBlock.BlockAlignment.valueOf(align), parsePosition(position))
+        val block = IRBlock(name, addressNum, IRBlock.BlockAlignment.valueOf(align), parsePosition(position))
         while(true) {
             line = lines.next()
             if(line.isBlank())
@@ -262,7 +261,7 @@ class IRFileReader(outputDir: Path, programName: String) {
             if(line=="</BLOCK>")
                 return block
             if(line.startsWith("<SUB ")) {
-                val sub = parseSubroutine(line, lines)
+                val sub = parseSubroutine(line, lines, variables)
                 block += sub
             } else if(line.startsWith("<ASMSUB ")) {
                 val sub = parseAsmSubroutine(line, lines)
@@ -289,23 +288,33 @@ class IRFileReader(outputDir: Path, programName: String) {
     }
 
     private fun parseAsmSubroutine(startline: String, lines: Iterator<String>): IRAsmSubroutine {
-        // <ASMSUB NAME=main.testasmsub ADDRESS=null POS=[examples/test.p8: line 14 col 6-11]>
-        // TODO parse more signature stuff once it's there.
+        // <ASMSUB NAME=main.testasmsub ADDRESS=null CLOBBERS=A,Y POS=[examples/test.p8: line 14 col 6-11]>
         val match = asmsubPattern.matchEntire(startline) ?: throw IRParseException("invalid ASMSUB")
-        val (scopedname, address, pos) = match.destructured
+        val (scopedname, address, clobbers, pos) = match.destructured
         var line = lines.next()
         val asm = parseInlineAssembly(line, lines)
         while(line!="</ASMSUB>")
             line = lines.next()
-        return IRAsmSubroutine(scopedname, parsePosition(pos), if(address=="null") null else address.toUInt(), asm.asm)
+        val clobberRegs = clobbers.split(',').map { CpuRegister.valueOf(it) }
+        // TODO parse this additional signature stuff once it's there.
+        val parameters = mutableListOf<IRAsmSubroutine.IRAsmSubParam>()
+        val returns = mutableListOf<Pair<DataType, RegisterOrStatusflag>>()
+        return IRAsmSubroutine(scopedname,
+            parsePosition(pos), if(address=="null") null else address.toUInt(),
+            clobberRegs.toSet(),
+            parameters,
+            returns,
+            asm.asm)
     }
 
-    private fun parseSubroutine(startline: String, lines: Iterator<String>): IRSubroutine {
+    private fun parseSubroutine(startline: String, lines: Iterator<String>, variables: List<StStaticVariable>): IRSubroutine {
         // <SUB NAME=main.start.nested.nested2 RETURNTYPE=null POS=[examples/test.p8: line 54 col 14-16]>
-        // TODO parse more signature stuff once it's there.
         val match = subPattern.matchEntire(startline) ?: throw IRParseException("invalid SUB")
         val (name, returntype, pos) = match.destructured
-        val sub = IRSubroutine(name, if(returntype=="null") null else parseDatatype(returntype, false), parsePosition(pos))
+        val sub = IRSubroutine(name,
+            parseParameters(lines, variables),
+            if(returntype=="null") null else parseDatatype(returntype, false),
+            parsePosition(pos))
         while(true) {
             val line = lines.next()
             if(line=="</SUB>")
@@ -328,6 +337,21 @@ class IRFileReader(outputDir: Path, programName: String) {
         return sub
     }
 
+    private fun parseParameters(lines: Iterator<String>, variables: List<StStaticVariable>): List<StStaticVariable> {
+        var line = lines.next()
+        if(line!="<PARAMS>")
+            throw IRParseException("missing PARAMS")
+        val params = mutableListOf<StStaticVariable>()
+        while(true) {
+            line = lines.next()
+            if(line=="</PARAMS>")
+                return params
+            val (datatype, name) = line.split(' ')
+            val dt = parseDatatype(datatype, datatype.contains('['))
+            params.add(variables.single { it.dt==dt && it.name==name})
+        }
+    }
+
     private fun parseCodeChunk(firstline: String, lines: Iterator<String>): IRCodeChunk? {
         if(firstline!="<C>") {
             if(firstline=="</SUB>")
diff --git a/intermediate/src/prog8/intermediate/IRFileWriter.kt b/intermediate/src/prog8/intermediate/IRFileWriter.kt
index b978abd9a..167ff348b 100644
--- a/intermediate/src/prog8/intermediate/IRFileWriter.kt
+++ b/intermediate/src/prog8/intermediate/IRFileWriter.kt
@@ -39,7 +39,9 @@ class IRFileWriter(private val irProgram: IRProgram) {
             }
             block.subroutines.forEach {
                 out.write("<SUB NAME=${it.name} RETURNTYPE=${it.returnType.toString().lowercase()} POS=${it.position}>\n")
-                // TODO rest of the signature
+                out.write("<PARAMS>\n")
+                it.parameters.forEach { param -> out.write("${getTypeString(param)} ${param.scopedName.joinToString(".")}\n") }
+                out.write("</PARAMS>\n")
                 it.chunks.forEach { chunk ->
                     if(chunk is IRInlineAsmChunk) {
                         writeInlineAsm(chunk)
@@ -54,8 +56,9 @@ class IRFileWriter(private val irProgram: IRProgram) {
                 out.write("</SUB>\n")
             }
             block.asmSubroutines.forEach {
-                out.write("<ASMSUB NAME=${it.name} ADDRESS=${it.address} POS=${it.position}>\n")
-                // TODO rest of the signature
+                val clobbers = it.clobbers.joinToString(",")
+                out.write("<ASMSUB NAME=${it.name} ADDRESS=${it.address} CLOBBERS=$clobbers POS=${it.position}>\n")
+                // TODO rest of the signature:  RETURNS = it.returns
                 out.write("<INLINEASM POS=${it.position}>\n")
                 out.write(it.assembly.trimStart('\n').trimEnd(' ', '\n'))
                 out.write("\n</INLINEASM>\n</ASMSUB>\n")
@@ -130,6 +133,22 @@ class IRFileWriter(private val irProgram: IRProgram) {
         out.write("</MEMORYSLABS>\n")
     }
 
+    private fun getTypeString(dt : DataType): String {
+        return when(dt) {
+            DataType.UBYTE -> "ubyte"
+            DataType.BYTE -> "byte"
+            DataType.UWORD -> "uword"
+            DataType.WORD -> "word"
+            DataType.FLOAT -> "float"
+            DataType.ARRAY_UB, DataType.STR -> "ubyte[]"
+            DataType.ARRAY_B -> "byte[]"
+            DataType.ARRAY_UW -> "uword[]"
+            DataType.ARRAY_W -> "word[]"
+            DataType.ARRAY_F -> "float[]"
+            else -> throw InternalCompilerException("weird dt")
+        }
+    }
+
     private fun getTypeString(memvar: StMemVar): String {
         return when(memvar.dt) {
             DataType.UBYTE -> "ubyte"
diff --git a/intermediate/src/prog8/intermediate/IRProgram.kt b/intermediate/src/prog8/intermediate/IRProgram.kt
index e61327604..5c39c575b 100644
--- a/intermediate/src/prog8/intermediate/IRProgram.kt
+++ b/intermediate/src/prog8/intermediate/IRProgram.kt
@@ -1,11 +1,8 @@
 package prog8.intermediate
 
+import prog8.code.StStaticVariable
 import prog8.code.SymbolTable
-import prog8.code.ast.PtBlock
-import prog8.code.core.CompilationOptions
-import prog8.code.core.DataType
-import prog8.code.core.IStringEncoding
-import prog8.code.core.Position
+import prog8.code.core.*
 
 /*
 
@@ -25,6 +22,7 @@ PROGRAM:
         INLINEASM
         INLINEASM
         SUB
+            PARAMS
             INLINEASM
             INLINEASM
             C (CODE)
@@ -65,13 +63,19 @@ class IRProgram(val name: String,
 class IRBlock(
     val name: String,
     val address: UInt?,
-    val alignment: PtBlock.BlockAlignment,
+    val alignment: BlockAlignment,
     val position: Position
 ) {
     val subroutines = mutableListOf<IRSubroutine>()
     val asmSubroutines = mutableListOf<IRAsmSubroutine>()
     val inlineAssembly = mutableListOf<IRInlineAsmChunk>()
 
+    enum class BlockAlignment {
+        NONE,
+        WORD,
+        PAGE
+    }
+
     operator fun plusAssign(sub: IRSubroutine) {
         subroutines += sub
     }
@@ -80,8 +84,10 @@ class IRBlock(
 }
 
 class IRSubroutine(val name: String,
+                   val parameters: List<StStaticVariable>,  // NOTE: these are the same objects as their occurrences as variables in the symbol table
                    val returnType: DataType?,
                    val position: Position) {
+
     val chunks = mutableListOf<IRCodeChunkBase>()
 
     init {
@@ -97,6 +103,9 @@ class IRSubroutine(val name: String,
 class IRAsmSubroutine(val name: String,
                       val position: Position,
                       val address: UInt?,
+                      val clobbers: Set<CpuRegister>,
+                      val parameters: List<IRAsmSubParam>,
+                      val returns: List<Pair<DataType, RegisterOrStatusflag>>,
                       val assembly: String) {
     val lines = mutableListOf<IRCodeLine>()
 
@@ -106,6 +115,8 @@ class IRAsmSubroutine(val name: String,
         if(name.startsWith("main.main."))
             throw IllegalArgumentException("subroutine name invalid main prefix: $name")
     }
+
+    class IRAsmSubParam(val name: String, val dt: DataType, val reg: RegisterOrStatusflag)
 }
 
 sealed class IRCodeLine