diff --git a/etc/assembler-test.usm b/etc/assembler-test.usm
new file mode 100644
index 0000000..03f1750
--- /dev/null
+++ b/etc/assembler-test.usm
@@ -0,0 +1,14 @@
+%swap2 { SWP SWP2 }
+%swap4 { swap2 swap2 }
+%swap8 { swap4 swap4 }
+%swap16 { swap8 swap8 }
+
+%NOPa2r { NOP2r }
+
+;Hello { world 2 there 1 testing 10 }
+
+( references to variables (e.g. Hello.world) not implemented yet )
+
+NOPa2r
+swap16
+
diff --git a/projects/software/assembler.usm b/projects/software/assembler.usm
index 0e8965f..5d7de4c 100644
--- a/projects/software/assembler.usm
+++ b/projects/software/assembler.usm
@@ -3,6 +3,7 @@
 
 %HCF { #0000 DIV }
 %SHORT_FLAG { #20 }
+%RETURN_FLAG { #40 }
 
 ( devices )
 
@@ -23,19 +24,49 @@
 	,assembler-heap-start =assembler.heap
 	#0070 =assembler.addr
 
-	,$token ^assemble-token JSR
-	,$token2 ^assemble-token JSR
-	,$token3 ^assemble-token JSR
-	,$token4 ^assemble-token JSR
-	,$token5 ^assemble-token JSR
-	~assembler.state
+	,$read-filename =File.name
+	#1000 =File.length
+	#f000 =File.load
+
+	#f000 #1000 ^assemble-chunk JSR
 	HCF
 
-	$token [ 3b Hello 00 ]
-	$token2 [ 7b 00 ]
-	$token3 [ testing 00 ]
-	$token4 [ 30 00 ]
-	$token5 [ 7d 00 ]
+	$read-filename [ etc/assembler-test.usm 00 ]
+
+@assemble-chunk ( ptr* len* -- 00 if EOF found in chunk
+                            OR assembled-up-to-ptr* 01 if reached end of chunk )
+	OVR2 ADD2 STH2
+	#0001 SUB2
+
+	$per-token
+	DUP2 STH2
+
+	$loop
+	#0001 ADD2
+	DUP2 PEK2
+	#20 GTH ^$loop JNZ
+
+	DUP2 OVR2r STH2r LTS2 ^$valid JNZ
+	SWP2r POP2r POP2
+	STH2r #0001 ADD2
+	#01 JMP2r
+
+	$valid
+	DUP2 PEK2 #00 OVR2 POK2
+	STH2r #0001 ADD2 ^assemble-token JSR
+	^$per-token JNZ
+
+	POP2 POP2r #00 JMP2r
+
+@assemble-macro ( macro-ptr* -- )
+	DUP2 ,strlen JSR2 DUP2 #0000 EQU2 ^$end JNZ
+	OVR2 ^assemble-token JSR
+	ADD2 #0001 ADD2
+	^assemble-macro JMP
+
+	$end
+	POP2 POP2
+	JMP2r
 
 @assemble-token ( string-ptr* -- )
 	( get location of tree )
@@ -628,6 +659,7 @@
 	$end
 	DUP ^$loop JNZ
 	POP
+	~assembler.state #0c ORA =assembler.state
 	JMP2r
 
 (
@@ -656,7 +688,7 @@
 	JMP2r
 
 @macro-}   [ 0000 ]    [ 0000 ]    [ 7d ]
-	~assembler.heap DUP2 #f0 ROT ROT POK2
+	~assembler.heap DUP2 #00 ROT ROT POK2
 	#0001 ADD2 =assembler.heap
 	~assembler.state #fc AND =assembler.state
 	JMP2r
@@ -687,10 +719,40 @@
 	JMP2r
 
 @normal-main
-	,$string =Console.string
-	HCF
+	~assembler.token
+	,opcodes-tree OVR2 #03 ,traverse-tree JSR2
+	^$not-opcode JNZ
 
-	$string [ Not 20 implemented 0a 00 ]
+	,opcodes-asm SUB2 #0007 DIV2
+	SWP2 #0003 ADD2
+	$flags
+	DUP2 PEK2
+	DUP #00 EQU ^$end-flags JNZ
+	DUP #32 NEQ ^$not-two JNZ
+	POP SWP2 SHORT_FLAG ORA SWP2 #0001 ADD2 ^$flags JMP
+	$not-two
+	DUP #72 NEQ ^$not-r JNZ
+	POP SWP2 RETURN_FLAG ORA SWP2 #0001 ADD2 ^$flags JMP
+	$not-r
+	POP POP2 ~assembler.token SWP2
+	^$not-opcode JMP
+
+	$end-flags
+	POP POP2
+	,write-byte JSR2
+	POP
+	JMP2r
+
+	$not-opcode
+	POP2
+	,macro-tree SWP2 #ff ,traverse-tree JSR2
+	^$not-macro JNZ
+	,assemble-macro JMP2 ( tail call )
+
+	$not-macro
+	( FIXME complain about bad opcode / nonexistent macro )
+	POP2
+	JMP2r
 
 (
 	Here's the big set of trees relating to labels. Starting from l-root, all