diff --git a/make.py b/make.py
index 43e4d293f..6591ceee4 100755
--- a/make.py
+++ b/make.py
@@ -162,7 +162,7 @@ CPU type:  {}
 					write_to_file(os.path.join(genhdir, "sdram_phy.h"), boilerplate + sdram_phy_header)
 		mem_header = cpuif.get_mem_header(memory_regions, getattr(soc, "flash_boot_address", None))
 		write_to_file(os.path.join(genhdir, "mem.h"), boilerplate + mem_header)
-		csr_header = cpuif.get_csr_header(csr_regions, soc.interrupt_map)
+		csr_header = cpuif.get_csr_header(csr_regions, soc.get_constants())
 		write_to_file(os.path.join(genhdir, "csr.h"), boilerplate + csr_header)
 
 	if actions["build-csr-csv"]:
diff --git a/misoclib/soc/__init__.py b/misoclib/soc/__init__.py
index f900dac91..ada3e9e4e 100644
--- a/misoclib/soc/__init__.py
+++ b/misoclib/soc/__init__.py
@@ -64,6 +64,7 @@ class SoC(Module):
 
 		self._memory_regions = [] # list of (name, origin, length)
 		self._csr_regions = [] # list of (name, origin, busword, csr_list/Memory)
+		self._constants = [] # list of (name, value)
 
 		self._wb_masters = []
 		self._wb_slaves = []
@@ -159,6 +160,16 @@ class SoC(Module):
 	def get_csr_regions(self):
 		return self._csr_regions
 
+	def add_constant(self, name, value):
+		self._constants.append((name, value))
+
+	def get_constants(self):
+		r = []
+		for name, interrupt in sorted(self.interrupt_map.items(), key=itemgetter(1)):
+			r.append((name.upper() + "_INTERRUPT", interrupt))
+		r += self._constants
+		return r
+
 	def do_finalize(self):
 		registered_mems = {regions[0] for regions in self._memory_regions}
 		if self.cpu_type != "none":
diff --git a/misoclib/soc/cpuif.py b/misoclib/soc/cpuif.py
index 737d2c71a..48d77604e 100644
--- a/misoclib/soc/cpuif.py
+++ b/misoclib/soc/cpuif.py
@@ -68,7 +68,7 @@ def _get_rw_functions(reg_name, reg_base, nwords, busword, read_only):
 		r += "}\n"
 	return r
 
-def get_csr_header(regions, interrupt_map):
+def get_csr_header(regions, constants):
 	r = "#ifndef __GENERATED_CSR_H\n#define __GENERATED_CSR_H\n#include <hw/common.h>\n"
 	for name, origin, busword, obj in regions:
 		if isinstance(obj, Memory):
@@ -80,12 +80,11 @@ def get_csr_header(regions, interrupt_map):
 				nr = (csr.size + busword - 1)//busword
 				r += _get_rw_functions(name + "_" + csr.name, origin, nr, busword, isinstance(csr, CSRStatus))
 				origin += 4*nr
-			try:
-				interrupt_nr = interrupt_map[name]
-			except KeyError:
-				pass
-			else:
-				r += "#define "+name.upper()+"_INTERRUPT "+str(interrupt_nr)+"\n"
+
+	r += "\n/* constants */\n"
+	for name, value in constants:
+		r += "#define " + name + " " + str(value) + "\n"
+
 	r += "\n#endif\n"
 	return r