IEC PAS 63693:2026

IEC PAS 63693 ®
Edition 1.0 2026-06
PUBLICLY AVAILABLE
SPECIFICATION
Industrial networks - Fieldbus specifications - WiTSnet

ICS 25.040.40  ISBN 978-2-8327-1252-8

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CONTENTS
FOREWORD . 11
INTRODUCTION . 13
1 Scope . 14
1.1 General . 14
1.2 Specifications . 14
1.3 Applicability . 15
1.4 Conformance . 15
2 Normative references . 15
3 Terms and definitions, symbols, abbreviated terms and conventions . 16
3.1 Reference model terms and definitions . 16
3.1.1 ISO/IEC 7498-1:1994. 16
3.1.2 ISO/IEC 8824-1:2021. 17
3.1.3 ISO/IEC 9545:1994 . 17
3.1.4 ISO/IEC 10731:1994 . 18
3.1.5 ISO/IEC 19501:2005 . 18
3.2 Service convention terms and definitions . 18
3.3 Additional WiTSnet terms and definitions . 19
3.4 Symbols and abbreviations . 25
3.5 Conventions for service . 27
3.5.1 Overview . 27
3.5.2 General conventions . 27
3.5.3 Conventions for class definitions . 28
3.5.4 Conventions for service definitions . 29
3.6 Conventions for protocol . 30
3.6.1 General concept . 30
3.6.2 Abstract syntax conventions . 30
3.6.3 Convention for the encoding of reserved bits and octets . 32
3.6.4 Conventions for the common coding of specific field octets. 32
3.6.5 Primitive conventions . 33
3.6.6 State machine conventions . 33
4 WTSn system architecture . 34
4.1 Characteristic elements . 34
4.2 Architecture of an A-Device . 36
4.3 Structure of FAL . 38
4.4 Data types and encoding rules . 42
4.4.1 General description of data types and encoding rules . 42
4.4.2 Transfer syntax for bit sequences for enumeration . 42
4.4.3 Unsigned Integer . 43
4.4.4 Signed Integer . 44
4.4.5 Octet String . 45
4.4.6 Visible String . 45
4.4.7 UnicodeString . 45
5 UnicodeString sequence of universal coded characterWTSn data-link layer service
definition . 45
5.1 Overview . 45
5.2 Mailbox access . 46
5.2.1 Access of remote DLS-user . 46
5.2.2 Access of local DLS-user . 48
5.3 Buffer access . 50
5.3.1 Access of remote DLS-user . 50
5.3.2 Access of local DLS-user . 52
5.4 Extended Buffer access . 53
5.4.1 Access of remote DLS-user . 53
5.4.2 Access of local DLS-user . 55
5.5 Queue access . 57
5.5.1 Access of remote DLS-user . 57
5.5.2 Access of local DLS-user . 59
5.6 Open Queue access . 60
5.6.1 General model of open Queue (OQUE) . 60
5.6.2 Access of remote DLS-user . 60
5.6.3 Access of local DLS-user . 62
5.7 Attribute access . 63
5.7.1 Special Conditions of the Attribute Access . 63
5.7.2 Access of remote DLS-user . 63
5.7.3 Access of local DLS-user . 65
6 WTSn data-link layer protocol specification . 66
6.1 Overview of the DL-protocol . 66
6.1.1 A-Node structure and Topology . 66
6.1.2 A-Node access . 69
6.1.3 DL discovery and configuration . 70
6.1.4 Relay and transit function . 71
6.1.5 Error detection and recovery . 72
6.1.6 Time control . 73
6.1.7 DLS-user interaction . 74
6.2 Transfer Syntax . 87
6.2.1 General description of transfer syntax and encoding rules . 87
6.2.2 Ethernet DLPDU structure . 87
6.2.3 WTSn Frame structure . 90
6.2.4 Specific TLVs inside LLDPDU . 119
6.3 Attribute . 122
6.3.1 Type, Identification and Addressing Information . 122
6.3.2 Port specific parameters including PhL parameters. 124
6.3.3 LLDP parameters . 126
6.3.4 DLS-user object parameter . 128
6.3.5 Statistics . 140
6.3.6 Event parameter . 141
6.3.7 Synchronization . 142
6.3.8 Schedule parameter . 144
6.4 DLS-user interface . 146
6.4.1 Overview . 146
6.4.2 Attribute access type . 147
6.4.3 Queue access type . 147
6.4.4 Mailbox access type . 147
6.4.5 Buffer access type . 158
6.4.6 Extended Buffer access type . 174
6.5 FDL Protocol state machines . 185
6.5.1 Overview of A-Node DL state machines . 185
6.5.2 General definitions for an Ethernet link segment operation . 185
6.5.3 Implementation option with a single Port . 186
6.5.4 Port Receive state machines (PRM) . 186
6.5.5 Relay, transit and scheduling state machines (RTSM) . 186
6.5.6 Port Transmit state machines (PTM) . 207
6.5.7 Subframe processing state machine (SFPM) . 209
6.5.8 Discovery state machines . 212
6.5.9 Synchronization . 222
7 WTSn application layer service definition. 229
7.1 Overview . 229
7.2 Data type ASE . 230
7.2.1 General . 230
7.2.2 Formal definition of data type objects . 230
7.2.3 FAL defined data types . 230
7.2.4 Data type ASE service specification. 236
7.3 Communication model specification . 236
7.3.1 Concepts . 236
7.3.2 Modular device ASE . 237
7.3.3 AR ASE . 252
7.3.4 Discovery ASE . 258
8 WTSn application layer protocol specification . 267
8.1 Coding of PDU elements . 267
8.1.1 APDU structure. 267
8.1.2 Common APDU elements . 267
8.1.3 Transfer Data . 271
8.1.4 Variable Attributes and Definition . 273
8.1.5 Discovery . 276
8.1.6 Exchange of Process Elements . 277
8.1.7 AR Control APDU . 278
8.1.8 IPv4Encapsulation . 281
8.2 AR handling . 282
8.2.1 General . 282
8.2.2 Primitive definitions . 284
8.2.3 AR State Machine . 286
8.3 Special elements in the data transmission . 293
8.3.1 General Rules for data allocation in packets . 293
8.3.2 Fragmentation . 294
8.3.3 Isochronous Interaction . 303
8.4 Modelling of management functions . 306
8.4.1 Overview . 306
8.4.2 Synchronization management . 306
8.4.3 Identification . 307
8.4.4 Topology Management . 308
8.4.5 Scheduling . 310
8.4.6 Event Monitoring . 313
8.5 Open protocol transmission. 314
8.5.1 Principles of Operation . 314
8.5.2 Using MAC Address Transfer . 314
8.5.3 Identification and assignment of TNA . 315
8.5.4 Actions on the edge of WTSn networks . 317
8.5.5 Relationship to management . 317
8.5.6 Access to object model . 318
8.6 SHIM . 318
8.6.1 General . 318
8.6.2 Handling . 318
8.7 Multiple A-Controller or A-Device instances in an A-Node . 319
8.7.1 General . 319
8.7.2 Multiple A-Controllers . 319
8.7.3 Multiple A-Devices with separate Ports . 319
8.7.4 Multiple A-Devices without separate Ports . 319
Bibliography . 320

Figure 1 – Common structure of specific fields . 32
Figure 2 – Structure of an A-Device/A-Node . 37
Figure 3 – AL structure of an A-Device . 42
Figure 4 – Set of 2 port A-Devices connected to an A-Controller . 67
Figure 5 – Structure of A-Nodes with transit ports within a network . 67
Figure 6 – Structure with subsection ring and loops . 68
Figure 7 – Structure with redundant A-Controller connection . 69
Figure 8 – Loopback and One-way method . 70
Figure 9 – Mailbox interactions . 78
Figure 10 – Mailbox unidirectional interactions . 79
Figure 11 – Buffer interaction from A-Controller to A-Device . 80
Figure 12 – Buffer interaction from A-Device to A-Controller . 81
Figure 13 – Input XBUF with successful previous transaction . 82
Figure 14 – Input XBUF with previous transaction failed . 83
Figure 15 – Output XBUF with successful previous transaction . 84
Figure 16 – Output XBUF with previous transaction failed . 85
Figure 17 – Aggregation of DL objects into a single Command Execution List . 86
Figure 18 – WTSn elements in an Ethernet packet . 87
Figure 19 – RTM components . 187
Figure 20 – Structure of an interval . 204
Figure 21 – PTM components . 208
Figure 22 – Structure of a single transmit queue . 208
Figure 23 – TNA incremental assignment . 213
Figure 24 – Model of clock synchronization . 224
Figure 25 – Measurement of the link delay . 225
Figure 26 – Determination of the Neighbor Frequency Difference . 226
Figure 27 – Distribution of startup parameters . 228
Figure 28 – Sequence of AR state interaction . 283
Figure 29 – AR state diagram . 286
Figure 30 – Example mapping steps of process elements . 293
Figure 31 – APDU types . 294
Figure 32 – Sequence of MBX interaction with request fragmentation . 295
Figure 33 – Sequence of MBX interaction with response fragmentation . 296
Figure 34 – Sequence of XBUF interaction with fragmentation . 297
Figure 35 – FRSM States . 297
Figure 36 – Isochronous Interactions . 304
Figure 37 – Interaction structure . 305
Figure 38 – Identification of a WTSn network . 308
Figure 39 – SHIM example . 318

Table 1 – PDU element description example . 31
Table 2 – Example attribute description . 32
Table 3 – State machine layout . 34
Table 4 – Description of state machine elements . 34
Table 5 – Characteristic features of WTSn DL protocol . 35
Table 6 – Transfer syntax for bit sequences . 43
Table 7 – Transfer syntax for Unsigned data types . 44
Table 8 – Transfer syntax for Integer data types . 45
Table 9 – DL-MBXwrite . 46
Table 10 – DL-MBXread. 47
Table 11 – DL-MBXset . 48
Table 12 – DL-MBXget . 49
Table 13 – DL-BUFwrite . 50
Table 14 – DL-BUFread . 51
Table 15 – DL-BUFset . 52
Table 16 – DL-BUFget . 52
Table 17 – DL-XBUFwrite . 53
Table 18 – DL-XBUFread . 54
Table 19 – DL-XBUFset . 55
Table 20 – DL-XBUFget . 56
Table 21 – DL-QUEwrite . 57
Table 22 – DL-QUEread. 58
Table 23 – DL-QUEset . 59
Table 24 – DL-QUEget . 59
Table 25 – DL-OQUEtransfer . 61
Table 26 – DL-OQUEset . 62
Table 27 – DL-OQUEget . 62
Table 28 – DL-REGwrite . 63
Table 29 – DL-REGread. 64
Table 30 – DL-ATTset . 65
Table 31 – DL-ATTget. 66
Table 32 – Types of Communication Relationship (CR) . 75
Table 33 – Command Execution List (CEL) description . 86
Table 34 – Command Execution List in an A-Node . 86
Table 35 – WTSn frame inside an Ethernet packet . 87
Table 36 – WTSn frame inside a UDP PDU . 88
Table 37 – LLDP frame inside an Ethernet frame . 89
Table 38 – FCS octets of an erroneous Packet . 90
Table 39 – WTSn Frame common header structure . 91
Table 40 – TNA Definition . 92
Table 41 – WTSn FrameA structure containing WTSn PDU . 93
Table 42 – Buffer Read (BFRD) . 94
Table 43 – Buffer Write (BFWT) . 95
Table 44 – Buffer multiple Write (BFmW) . 97
Table 45 – Buffer Read and multiple Write (BFRmW) . 98
Table 46 – Buffer Read Write (BFRW) . 100
Table 47 – Extended Buffer Read (XBRD) . 101
Table 48 – Extended Buffer Write (XBWT) . 103
Table 49 – Mailbox Read (MBRD) . 105
Table 50 – Mailbox Write (MBWT). 106
Table 51 – Queue Read (QURD). 108
Table 52 – Queue Write (QUWT) . 109
Table 53 – Command Execution List (CEL) . 111
Table 54 – Register Read (RGRD) . 112
Table 55 – Register Write (RGWT). 114
Table 56 – Register multiple Write (RGmW) . 115
Table 57 – Register Read and multiple Write (RGRmW) . 116
Table 58 – Register Mask Write (RGmsWT) . 118
Table 59 – TLV elements . 119
Table 60 – WTSn identification and TNA setup . 120
Table 61 – WTSn topology subtree . 121
Table 62 – Node information . 123
Table 63 – Link control/status . 125
Table 64 – LLDP attributes . 126
Table 65 – CR-bundle attributes . 129
Table 66 – Mailbox attributes . 131
Table 67 – Buffer attributes. 132
Table 68 – XBuffer attributes . 135
Table 69 – Queue attributes . 137
Table 70 – CEL attributes . 139
Table 71 – Multicast attributes . 140
Table 72 – TX/RX counters . 140
Table 73 – Additional counters . 141
Table 74 – Event structure . 141
Table 75 – Link local measurement . 143
Table 76 – Clock parameter . 144
Table 77 – Interval layout . 145
Table 78 – Interval specification . 145
Table 79 – Scheduler packet list attributes . 146
Table 80 – Primitives issued by SFPM to MBX . 148
Table 81 – Primitives issued by MBX to SFPM . 148
Table 82 – Primitives issued by DLS-user to MBX . 149
Table 83 – Primitives issued by MBX to DLS-user . 149
Table 84 – Parameters of the primitives . 149
Table 85 – MBX Variables . 150
Table 86 – MBX state table . 150
Table 87 – MBXr Variables . 154
Table 88 – MBXr state table . 155
Table 89 – Primitives issued by SFPM to OBUF . 159
Table 90 – Primitive issued by OBUF to SFPM . 159
Table 91 – Primitive issued by DLS-user to OBUF . 159
Table 92 – Primitive issued by OBUF to DLS-user . 159
Table 93 – Parameters of the primitives . 160
Table 94 – OBUF Variables . 160
Table 95 – Transfer of Output Buffers overview . 160
Table 96 – OBUF state table . 161
Table 97 – Primitives issued by SFPM to OBUFr . 163
Table 98 – Primitives issued by OBUFr to SFPM . 163
Table 99 – Primitives issued by DLS-user to OBUFr . 163
Table 100 – Primitives issued by OBUFr to DLS-user . 163
Table 101 – OBUFr Variables and Functions . 164
Table 102 – Transfer of redundant Output Buffers overview . 164
Table 103 – OBUFr state table . 165
Table 104 – Primitives issued by SFPM to IBUF . 167
Table 105 – Primitive issued by IBUF to SFPM . 167
Table 106 – Primitive issued by DLS-user to IBUF . 168
Table 107 – Primitive issued by IBUF to DLS-user . 168
Table 108 – Parameters of the primitives . 168
Table 109 – IBUF Variables . 169
Table 110 – Transfer of Input Buffers overview . 169
Table 111 – IBUF state table . 170
Table 112 – Primitives issued by SFPM to IBUFr . 171
Table 113 – Primitives issued by IBUFr to SFPM . 172
Table 114 – IBUFr Variables and Functions . 172
Table 115 – Transfer of redundant Input Buffers overview . 173
Table 116 – IBUFr state table . 173
Table 117 – Primitives issued by SFPM to OXBUF . 175
Table 118 – Primitive issued by OXBUF to SFPM . 175
Table 119 – Primitive issued by DLS-user to OXBUF . 176
Table 120 – Primitive issued by OXBUF to DLS-user . 176
Table 121 – Parameters of the primitives . 176
Table 122 – OXBUF Variables . 177
Table 123 – OXBUF state table. 177
Table 124 – Primitives issued by SFPM to IXBUF . 180
Table 125 – Primitive issued by IXBUF to SFPM . 180
Table 126 – Primitive issued by DLS-user to IXBUF . 180
Table 127 – Primitive issued by IXBUF to DLS-user . 181
Table 128 – Parameters of the primitives . 181
Table 129 – IXBUF Variables . 181
Table 130 – IXBUF state table . 182
Table 131 – Primitives issued by PRM to Parser . 188
Table 132 – Primitives between Parser and DelayFifo . 188
Table 133 – Primitives between Parser and TNA Handler . 188
Table 134 – Primitive between Parser and SFPM . 188
Table 135 – Primitive between Parser and Frame Conversion . 189
Table 136 – Primitive between SFPM and OutboundFifo . 189
Table 137 – Primitive between Frame Conversion and OutboundFifo . 189
Table 138 – Parameters of the primitives . 189
Table 139 – Parser Variables . 190
Table 140 – Parser decision list of Ethernet Packet structure . 191
Table 141 – WTSn Frame common elements decision list . 193
Table 142 – Parameter and Functions . 196
Table 143 – WTSn SubFrame decision list . 196
Table 144 – Determination of the target port . 198
Table 145 – Redundant Transmission Variables and Functions . 199
Table 146 – Determination of the target port with redundancy . 200
Table 147 – Parameter of an interval specification . 204
Table 148 – Example Interval layout . 206
Table 149 – Example parameter set of an interval specification . 207
Table 150 – Default multicast setting . 209
Table 151 – Functions for checking subframe information . 209
Table 152 – Checking Subfram
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