diff --git a/mesecons_microcontroller/init.lua b/mesecons_microcontroller/init.lua
index 2e11afa..05384da 100644
--- a/mesecons_microcontroller/init.lua
+++ b/mesecons_microcontroller/init.lua
@@ -332,7 +332,8 @@ yc.parse_get_eeprom_param = function(cond, starti)
 	local addr
 	while s ~= "" do
 		s = string.sub(cond, i, i)
-		if string.find("0123456789", s) == nil or s == "" then
+		local b = s:byte()
+		if s == "" or 48 > b or b > 57 then
 			addr = string.sub(cond, starti, i-1) -- i: last number i+1 after last number
 			return addr, i
 		end
@@ -419,13 +420,16 @@ yc.command_sbi = function(params, eeprom, L, Lv)
 
 	if status == nil then return nil, nil end
 
-	if string.find("ABCD", params[1])~=nil and #params[1]==1 then --is a port
-		if status == "1" then
-			Lv = yc.set_portstate (params[1], true,  Lv)
-		else
-			Lv = yc.set_portstate (params[1], false, Lv)
+	if #params[1]==1 then
+		local b = params[1]:byte()
+		if 65 <= b and b <= 68 then -- is a port
+			if status == "1" then
+				Lv = yc.set_portstate (params[1], true,  Lv)
+			else
+				Lv = yc.set_portstate (params[1], false, Lv)
+			end
+			return eeprom, Lv;
 		end
-		return eeprom, Lv;
 	end
 
 	--is an eeprom address