diff --git a/specs.py b/specs.py
index 5653c25..0da6602 100644
--- a/specs.py
+++ b/specs.py
@@ -499,15 +499,19 @@ profinet_rt="Frame ID:16,User Data:80,Cycle Counter:16,Data Status:8,Transfer St
 
 dnp3="Start:16,Length:8,Control:8,Destination Address:16,Source Address:16,CRC:16,User Data 1:128,CRC 1:16,User Data 2:112,CRC 2:16"
 
-tsap="Type:8,Slot:5,Rack:3"
+tsap="Type:8,Slot:5,Rack:3?bits=16"
 
 cotp_cr="Length:8,PDU Type:8, Destination Reference:16, Source Reference:16,Class/Options:8,Param. Code:8,Param. Length:8,Param.:88"
 
-cotp_dt="Length:8,PDU Type:8,Num. & LDU:8"
+cotp_dt="Length:8,PDU Type:8,Num. & LDU:8?bits=24"
 
 cotp_dr="Length:8,PDU Type:8, Destination Reference:16, Source Reference:16,Cause:8"
 
-s7="Protocol ID:8,ROSCTR:8,Reserved:16,Request ID:16,Parameter Length:16,Data Length:16,Error Code (only ROSCTR 3):16,Function Code:8,Item Count:8"
+s7_header="Protocol ID:8,ROSCTR:8,Reserved:16,Request ID:16,Parameter Length:16,Data Length:16,Error Code (only ROSCTR 3):16,Function Code:8,Item Count:8?bits=16"
+
+s7_item="Var Type:8,Var Length:8,Syntax ID:8,Transport Size:8,Length:16,DB Number:16,Area:8,Address:24"
+
+s7_data="Return Code:8,Transport Size:8,Data Length:16"
 
 #      0                   1
 #      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
@@ -749,8 +753,10 @@ protocols={"ethernet":ethernet,
            "profinet_rt":profinet_rt,
            "tsap":tsap,
            "dnp3":dnp3,
-           "s7":s7,
-           "cotp_cc":cotp_cr,
+           "s7_header":s7_header,
+           "s7_item":s7_item,
+           "s7_data":s7_data,
+           "cotp_cr":cotp_cr,
            "cotp_dt":cotp_dt,
            "cotp_dr":cotp_dr,
            "example":example,