Question 1

What is an I/O list?

Accepted Answer

An I/O list is the register of every input and output signal a control system reads from or writes to the field. Each row is one instrument signal with its tag, service, control loop, and signal class. It is the document that sizes the PLC or DCS and drives marshalling, wiring, and checkout. Tagsight builds it as a 14-column list extracted from the P&ID package.

Question 2

What columns does an I/O list have?

Accepted Answer

The Tagsight I/O list carries 14 columns: tag, service description, P&ID sheet, loop number, signal class, sub-class (BPCS or SIS), range, units, set point, trip or alarm value, cabinet, card slot, channel, and notes or revisions. The first columns come from the drawing, range and units from the datasheet, and cabinet, slot, and channel are assigned downstream during I/O allocation.

Question 3

What are the signal classes on an I/O list?

Accepted Answer

Each signal is classified as AI (analog input), AO (analog output), DI (discrete input), or DO (discrete output) per ISA 5.1. The signal class is what determines which controller card the point lands on, so it is the column the controls team uses to size the I/O hardware. You confirm the class on every row before it exports.

Question 4

What is the difference between BPCS and SIS rows on an I/O list?

Accepted Answer

The sub-class column separates Basic Process Control System (BPCS) points from Safety Instrumented System (SIS) points. IEC 61511 requires the safety function to be independent of basic control, so the SIS rows are split out to land on separate, independent I/O. Carrying the sub-class on every row lets the list be filtered into separate BPCS and SIS lists.

Question 5

What formats can an I/O list export to?

Accepted Answer

The I/O list exports to TIA Portal XML, Rockwell Studio 5000 L5X, a PLCCreator-compatible CSV, an Excel workbook, and the ISO 15926-based DEXPI interchange format. The tag and signal class travel into each export so the controls engineer imports one file rather than re-keying the list.

#	Column	Type	Origin	Description
01	Tag	string	drawing	Instrument tag per ISA 5.1 dialect. Instrument identifier as it appears on the drawing.
02	Service description	string	drawing	Process service the instrument measures or controls.
03	P&ID sheet	string	drawing	Source drawing number and revision. Traces every row back to its origin sheet.
04	Loop	integer	drawing	Control-loop number for grouping and loop-folder organisation.
05	Signal class	enum	drawing	AI, AO, DI, or DO per ISA 5.1. You confirm the class on every row before export.
06	Sub-class	enum	drawing	BPCS or SIS. Splits basic process control from safety per IEC 61511 separation.
07	Range	string	datasheet	Engineering range when the drawing or attached datasheet shows it.
08	Units	string	datasheet	Engineering units paired with the range, preserved exactly as on the drawing.
09	Set point	number	datasheet	Process set point when specified. Blank otherwise.
10	Trip / alarm	number	datasheet	Trip or alarm value for protective signals. Blank when not yet defined.
11	Cabinet	string	downstream	Marshalling cabinet ID. Owned by the controls engineer.
12	Card slot	string	downstream	PLC card slot assignment. Owned downstream during the I/O assignment pass.
13	Channel	integer	downstream	Channel number within the card slot. Same downstream pass.
14	Notes / revisions	string	audit	Revision marker, MOC reference, free-text note.

#	Column	Type	Origin	Description
01	Tag	string	drawing	Instrument tag per ISA 5.1 dialect. Instrument identifier as it appears on the drawing.
02	Service description	string	drawing	Process service the instrument measures or controls.
03	P&ID sheet	string	drawing	Source drawing number and revision. Traces every row back to its origin sheet.
04	Loop	integer	drawing	Control-loop number for grouping and loop-folder organisation.
05	Signal class	enum	drawing	AI, AO, DI, or DO per ISA 5.1. You confirm the class on every row before export.
06	Sub-class	enum	drawing	BPCS or SIS. Splits basic process control from safety per IEC 61511 separation.
07	Range	string	datasheet	Engineering range when the drawing or attached datasheet shows it.
08	Units	string	datasheet	Engineering units paired with the range, preserved exactly as on the drawing.
09	Set point	number	datasheet	Process set point when specified. Blank otherwise.
10	Trip / alarm	number	datasheet	Trip or alarm value for protective signals. Blank when not yet defined.
11	Cabinet	string	downstream	Marshalling cabinet ID. Owned by the controls engineer.
12	Card slot	string	downstream	PLC card slot assignment. Owned downstream during the I/O assignment pass.
13	Channel	integer	downstream	Channel number within the card slot. Same downstream pass.
14	Notes / revisions	string	audit	Revision marker, MOC reference, free-text note.

I/O list.

Read one of your own drawings.

Schema.

From drawing to PLC.

Vendor targets.

Run it on your drawings.

I/O list.

Read one of your own drawings.

Schema.

From drawing to PLC.

Vendor targets.

Run it on your drawings.

I/O list.

Read one of your own drawings.

Schema.

From drawing to PLC.

Vendor targets.

More on the I/O list.

Run it on your drawings.

I/O list.

Read one of your own drawings.

Schema.

From drawing to PLC.

Vendor targets.

More on the I/O list.

Run it on your drawings.