Signal Editor

What This Chapter Covers

This chapter describes the Signal editor, which edits the communication data dictionary — CAN and LIN frames, the six PDU kinds, I-Signals, and signal groups. It covers the screen layout, the editable fields for each item type, the bit layout preview, and how to edit initial values. The DBC and ARXML import and export procedures themselves belong to 13. Import and Export; this chapter goes only as far as explaining where their results appear on screen.

The intended reader writes a bus communication matrix, or reviews and edits an imported one. Open the project in PAIO before you start.

The Signal editor has no row under DESIGN in the EDITOR view. You open it from the System editor.

1. In the EDITOR view, click System under DESIGN. The System editor opens in the tab <project>:System.
2. Click Signal, the top icon of the strip at the left edge of the canvas. The Signal editor opens in a new tab, <project>:Signal.

Opening the Signal editor — ① System under DESIGN in the EDITOR view, ② the Signal icon at the top of the canvas's left icon strip

The editor saves to a single Signal model, design/SIGNAL.io.model. Terms that are easy to confuse, such as a signal's two names (I-Signal and System Signal), are collected in 19. Glossary.

7.1 Screen Layout

The editor consists of a protocol tab bar across the top and, below it, a list panel on the left and the Configuration panel taking the rest of the width.

The Signal editor on the CAN tab — ① protocol tabs, ② the CAN FRAMES list, ③ the Configuration form, ④ the PREVIEW and PDU REFERENCES tabs of the form's right column, ⑤ the SIGNALS table

Each area holds the following content.

Area	Content	Size
List (left)	The items on the current tab	Drag to resize
Configuration	The property form for the selected item. For a frame, an I-Signal I-PDU or an NM-PDU, the form has a right column with tabs (PREVIEW, plus a references tab for a frame), and the SIGNALS table spans the full width below the form	Takes the remaining width
SIGNAL GROUPS (right)	The signal group tree. On the SIGNAL tab only	Drag to resize

There is no separate Preview panel on the right of the CAN, LIN and PDU tabs. The bit layout is the PREVIEW tab inside the Configuration form (7.10).

A sash separates the form from the SIGNALS table. Drag it to change the form's height, and double-click it to return to the default height. The height is shared by every frame and PDU form and is screen state only; it is not saved to the file.

The SIGNALS table appears only on the frame tabs, and on the PDU tab when you select an I-Signal I-PDU or an NM-PDU. For the other PDU kinds and on the SIGNAL tab, the Configuration form uses the whole panel. The LIN event-triggered and sporadic frames are on a frame tab, but they show a read-only list instead of the table (7.7.2).

7.2 Protocol Tabs

The tab bar has four tabs. The CAN tab is active when the editor opens.

Tab	What you edit	List panel title
CAN	CAN and CAN FD frames	CAN FRAMES
LIN	LIN frames	LIN FRAMES
PDU	All six PDU kinds in one list	PDUS
SIGNAL	The signal (I-SIGNAL) dictionary	SIGNALS

There is no FlexRay tab and no Ethernet tab. You cannot edit FlexRay or Ethernet frames in this editor. Imported data is preserved in the file and is included in the export.

The NM-PDU has no tab of its own. You edit it on the combined PDU tab as one of the six PDU kinds.

7.3 The Left List Panel

Header Buttons

The list panel header has three buttons.

Button	Tooltip	Action
+	Add	Adds an item of the kind the current tab holds. On the PDU tab, a kind-selection menu opens
−	Remove	Deletes the selected items after a confirmation (7.6). Disabled when nothing is selected
⋯	Sort & Filter	Opens the filter and sort popover

Selecting Several Items

• Click an item to select it. Ctrl+click adds another item to the selection.
• Give the list focus and press Ctrl+A to select every item in the list.
• Give the list focus and press the arrow keys to move between items; the selection follows.

Search and the Status Bar

• The search field uses the placeholder Search.... It filters the list by matching what you type against item names as a case-insensitive substring.
• Press Esc in the search field to clear the search term and restore the full list.
• The status bar under the list reports the item count. Normally it shows only the total, as N items. It switches to M / N items only when a search term has reduced the result. A reduction from the PDU kind filter (7.4) does not use this fraction form, so with only a filter applied the status bar number can be larger than the number of rows you see.

Empty State and No Search Results

When the list is empty or the search returns nothing, the following text appears.

Situation	Text shown
The frame tab has no items at all	Add a frame
The PDU tab has no items at all	Add a PDU
The SIGNAL tab has no items at all	Add a signal
Items exist, but the search or filter matches none	No results found

Badges on List Items

Each list item carries a badge that depends on the tab.

Tab	Badge
CAN	The frame ID in hexadecimal (0x301)
LIN	The frame ID in hexadecimal (0x3F)
PDU	A kind tag on the left, the length on the right (8B)
SIGNAL	The bit length (8bit)

PDU tab list — ① the MUX kind tag of NewMuxPdu, ② its length badge 8B

The PDU kind tags are IS (I-Signal I-PDU), NM (NM-PDU), N (N-PDU), DCM (DCM-I-PDU), MUX (Multiplexed I-PDU), and GP (General Purpose PDU). Hover over a tag to see the full name in a tooltip. The list keeps the PDUs grouped in this kind order.

Items the tool generated automatically carry an additional origin badge. SOC marks an item derived from a service deployment (CP-SOA), and COM marks an SR-based COM-derived signal. The badge only reports origin; it does not lock the item for editing. You can rename, change, and delete a derived item like any other.

7.4 The More (⋯) Menu — Filter and Sort

Click the ⋯ button to open the popover. Clicking a check box inside it does not close the popover, so you can work through several items in a row. Press Esc to close the popover alone.

The filter and sort popover on the PDU tab — ① FILTER BY PDU TYPE with its All action, ② SORT BY (no ID option on the PDU tab)

The popover has the following sections.

Section	Shown when	Items
FILTER BY PDU TYPE	On the PDU tab only	A check box for each of the six PDU kinds, plus an All button on the right (tooltip Select All / Deselect All)
SORT BY	On every tab	Default (Added Order) / Name (A-Z) / ID

The ID sort option appears only on the frame tabs (CAN and LIN). The PDU tab and the SIGNAL tab have no IDs, so they offer the other two options only. Sorting changes the display order on screen; the order stored in the file stays as it was.

7.5 The Six PDU Kinds

Click + on the PDU tab to open a two-level menu. Hover over an entry on the left to expand its submenu on the right, then click a submenu entry to create a PDU of that kind. Click + again to close the menu.

Adding a PDU — ① the + button, ② Transport (TP) hovered, ③ its submenu N-PDU / DCM-I-PDU

The menu structure and the defaults for each kind are as follows.

Group	Entry	List tag	Defaults for a new item
Signal I-PDU	I-Signal I-PDU	IS	Name NewPdu, length 8 bytes, Unused Bit Pattern 0
Signal I-PDU	Multiplexed I-PDU	MUX	Name NewMuxPdu, length 8 bytes, Trigger Mode NONE, one empty Dynamic Part
Network Mgmt	NM-PDU	NM	Name NewNmPdu, length 8 bytes, NM Vote Information false
Transport (TP)	N-PDU	N	Name NewNPdu, length 8 bytes
Transport (TP)	DCM-I-PDU	DCM	Name NewDcmIPdu, length 8 bytes, Diag PDU Type DIAG-REQUEST
General Purpose	General Purpose PDU	GP	Name NewGeneralPurposePdu, length 8 bytes, Category SD

If the name already exists, the editor appends an underscore and a number to make it unique, giving NewPdu_1, NewPdu_2, and so on. Items of different kinds stay distinct even when they share a name, and the list compares both name and kind when it highlights the selection. A new PDU takes its place in the kind order of the list, so a new Multiplexed I-PDU appears above the General Purpose PDUs.

7.6 Adding and Deleting Items

Adding a Frame (CAN / LIN Tabs)

1. Select the tab and click +. The editor creates the new frame together with a PDU dedicated to that frame.
2. The new frame is selected automatically, and its property form appears in the Configuration panel.

The defaults per tab are as follows.

Tab	Frame defaults	PDU created alongside
CAN	Name NewFrame, DLC 8, Addressing standard, ID is the first free value from 0x100	NewFrame_Pdu, length 8 bytes
LIN	Name NewLinFrame, length 8, Checksum enhanced, ID is the first free value from 0x00	NewLinFrame_Pdu, length 8 bytes

Adding a Signal

There are two entry points for creating a signal.

1. The + on the SIGNAL tab — adds a signal to the dictionary only. Its name is NewSignal, with bit length 8, type uint, Factor 1, Offset 0, Min 0, Max 255, and initial value 0. It is not mapped to any PDU.
2. The + in the SIGNALS table header (tooltip Add Signal) — creates the signal and its mapping to the currently selected frame or PDU. The name takes the owner's name as a prefix, giving <ownerName>_Sig. The prefix is the frame name on a frame tab, and the name of the selected I-Signal I-PDU or NM-PDU on the PDU tab. If the frame references several PDUs, the signal is mapped to the first PDU that still has room.

When you add a signal through the table and the PDU is too short, the PDU length grows automatically. If the enlarged PDU exceeds the CAN frame's current DLC, the frame's DLC is raised automatically too. A PDU that no frame references has no byte limit applied.

When the frame is full, the add is silently ignored. If the bits already placed fill the frame's maximum byte count (64 bytes for CAN, 8 bytes for LIN), clicking + does nothing, and no message appears. The editor checks capacity and rejects the request before it creates the signal, so that unmapped signals do not pile up in the dictionary. Rearrange the frame composition or the PDU layout first.

Deleting

Select the items in the list, then click − or press Delete. A confirmation dialog opens first; click Delete to delete or Cancel to keep the items.

The confirmation dialog for one frame — ① Delete, ② Cancel

Selection	Dialog title	Message
One frame	Delete Frame	Are you sure you want to delete "<name>"?
Several frames	Delete Frames	Are you sure you want to delete these N Frames?, the names, and They are all deleted at once, along with everything attached to them.

Deleting several items at once is a single undo step.

The × at the end of a row in the SIGNALS table (tooltip Remove Signal) is different: it deletes the signal immediately, with no confirmation dialog. It does not just break the mapping: it removes the signal from the dictionary as well. There is no separate operation that detaches the mapping alone. To restore it, use EDIT › Undo (7.13).

Deleting also cleans up references.

• Deleting a frame or a PDU removes its name from the connector frame and PDU references (including the TX/RX PDU lists of General Purpose PDUs) in the IVC model (design/IVC.io.model), which is edited in the System editor. If the System editor is closed, the Signal editor edits the file on disk directly; if it is open, the System editor cleans up its own model. The NM-PDU is the exception: NM-PDU references live in the network management configuration of the IVC model and this path does not touch them.
• Deleting a signal removes every reference to it from the mappings of all PDUs and NM-PDUs.
• The data mapping references in the System model (design/SYSTEM.io.model) are cleaned up only when you delete through the × in the SIGNALS table. Deleting with − on the SIGNAL tab cleans up the dictionary and the PDU mappings only, and leaves the System data mapping references in place. Because the two paths behave differently, delete a signal that has data mappings from the table.

7.7 Configuration Panel — Editable Fields by Item Type

The panel header is always CONFIGURATION. With no item selected it shows a single line of guidance (Select a frame / Select a PDU / Select an NM-PDU / Select an N-PDU / Select a DCM-I-PDU / Select a General Purpose PDU / Select a Multiplexed I-PDU / Select a signal).

Field labels are painted in upper case (NAME, CAN ID); the tables below write them as they are spelled in the model. The fields marked Choice are drawn as a segmented button set, and the button labels are all upper case (standard → STANDARD, false → FALSE). The value stored in the model keeps the original spelling listed in the table. An empty Description field shows the hint Text.

7.7.1 CAN Frame

The left column holds the properties. The right column is a tab bar with PREVIEW (the default; the bit layout, 7.10) and PDU REFERENCES (7.8). The tab you choose stays selected when you select another frame.

The CAN frame form with the PDU REFERENCES tab — ① CAN ID with DEC / HEX, ② DLC, ③ Description with the hint Text, ④ the PDU REFERENCES table, ⑤ the PDU picker on the tab bar

Field	Form	Range and notes
Name	Text	AUTOSAR SHORT-NAME rules
Addressing	Choice	standard / extended
CAN ID	Hexadecimal input (DEC/HEX toggle)	standard allows 0x000 to 0x7FF, extended allows 0x00000000 to 0x1FFFFFFF. Change Addressing and the upper bound follows immediately
DLC	Searchable choice	16 options, 0 (0 bytes) through 15 (64 bytes). Values 9 to 15 are the CAN FD extensions (12/16/20/24/32/48/64 bytes)
Unused Bit Pattern	Segmented	0 / 1. This value is stored on the PDU the frame references, not on the frame
Description	Text

Changing the DLC also updates the length of the PDU the frame references to that byte count. This happens only when the frame references a single PDU; on a frame that references several PDUs, only the DLC changes. The clear (×) action on the DLC field is ignored, because the value is mandatory, and the previous value is restored.

7.7.2 LIN Frame

A LIN frame has the following editable fields. Which fields appear depends on the Frame Type.

Field	Form	Range and notes
Name	Text
Frame Type	Choice	unconditional / event-triggered / sporadic
Frame ID	Hexadecimal input (DEC/HEX toggle)	0x00 to 0x3F (the LIN 6 bits)
Length	Integer	1 to 8 bytes
Checksum	Choice	classic / enhanced (default enhanced). Not shown for a sporadic frame
Unused Bit Pattern	Segmented	0 / 1. Shown only for an unconditional frame
Collision Resolving Schedule	Searchable reference	Appears only when Frame Type is event-triggered. You pick from the LIN schedule tables in the IVC model; leave it empty and it reads (none) and no value is stored
Description	Text

The Frame Type also changes the right column and the area below it.

Frame Type	Right column tabs	Area below
unconditional	PREVIEW / PDU REFERENCES	SIGNALS table (editable)
event-triggered / sporadic	PREVIEW / FRAME REFERENCES	The signals of the referenced frames (read-only)

A sporadic frame is saved without a checksum. Changing a frame to event-triggered or sporadic releases the empty PDU it carried, and changing it back to unconditional gives it a new PDU.

By the LIN specification, event-triggered and sporadic frames carry no signals of their own; they take over the schedule slot of an unconditional frame. For these two kinds the editor therefore shows a read-only list instead of the editable table. Its header reads SIGNALS and has no +.

A LIN event-triggered frame — ① Frame Type, ② Collision Resolving Schedule (no Unused Bit Pattern field), ③ the FRAME REFERENCES tab and its picker, ④ the read-only SIGNALS list

The read-only list has the columns #, NAME, TYPE, BYTE-ORDER, START, LENGTH, and GROUP. For each referenced frame, a group row carrying the frame's name, ID, and length (NewLinFrame ID 0x00, Length 8) comes first, followed by that frame's signals.

To edit the signals themselves, go to the unconditional frame that owns them.

7.7.3 I-Signal I-PDU

An I-Signal I-PDU has the following editable fields.

Field	Form	Range and notes
Name	Text
Length (bytes)	Integer	1 or more
Unused Bit Pattern	Integer	0 to 255
Cycle Time (ms)	Decimal	0 or more. The model stores milliseconds and converts to seconds on ARXML export (the value ÷ 1000)
Transmission Mode	Choice	cyclic / event / not-used / none
Description	Text

The form has a right column with the PREVIEW tab only (the bit layout), and the SIGNALS table appears below the form.

7.7.4 NM-PDU

An NM-PDU has the following editable fields.

Field	Form	Range and notes
Name	Text
Length (bytes)	Integer
Unused Bit Pattern	Integer	0 to 255
NM Vote Information	Choice	false / true
NM Data Information	Choice	false / true
Description	Text

An NM-PDU can also carry UserData signals, so it offers the same PREVIEW tab and SIGNALS table as an I-Signal I-PDU.

7.7.5 N-PDU · DCM-I-PDU · General Purpose PDU

These three kinds hold no signal mappings. Their form has no right column (no PREVIEW tab) and no SIGNALS table; it takes the whole panel. The editable fields per kind are as follows.

Kind	Editable fields
N-PDU	Name, Length (bytes), Description
DCM-I-PDU	Name, Length (bytes), Diag PDU Type (DIAG-REQUEST / DIAG-RESPONSE), Description
General Purpose PDU	Name, Length (bytes), Category (a free-form keyword, SD on a new item), Description

7.7.6 Multiplexed I-PDU

The scalar properties are as follows.

Field	Form	Range and notes
Name	Text
Length (bytes)	Integer
Unused Bit Pattern	Integer	0 to 255
Has Dynamic Length	Choice	false / true
Selector Field Byte Order	Choice	MOST-SIGNIFICANT-BYTE-FIRST / MOST-SIGNIFICANT-BYTE-LAST / OPAQUE
Selector Field Length (bits)	Integer	1 to 16
Selector Field Start Position	Integer	0 or more
Trigger Mode	Choice	DYNAMIC-PART-TRIGGER / STATIC-PART-TRIGGER / STATIC-OR-DYNAMIC-PART-TRIGGER / NONE
Description	Text

Two nested editing areas follow below.

Area	Controls	When empty
DYNAMIC PARTS	The + in the header (tooltip Add Dynamic Part) adds a part, and each part has an × that removes it. Inside a part are the SEGMENTS (+ Segment) and ALTERNATIVES (+ Alternative) subtables	No dynamic parts
STATIC PARTS	The + in the header (tooltip Add Static Part) adds a part, and each part has an × (tooltip Remove Part). Each part has an I-PDU REF and a SEGMENTS subtable	No static parts

A Multiplexed I-PDU — ① DYNAMIC PARTS, ② the SEGMENTS subtable, ③ the ALTERNATIVES subtable, ④ STATIC PARTS, with Static Part 1 still missing its I-PDU Ref

Parts are numbered from 1, as in Dynamic Part 1 and Static Part 1. The subtables have the following columns, plus a row-delete × at the end of each row.

Subtable	Columns
SEGMENTS	BYTE ORDER (MOST-SIGNIFICANT-BYTE-FIRST / MOST-SIGNIFICANT-BYTE-LAST / OPAQUE), LENGTH, POSITION
ALTERNATIVES	I-PDU REF, SELECTOR CODE, INITIAL (a check box)

The I-PDU REF of a static part is a required reference. While it is empty, the field is painted red and reads I-PDU Ref is required.

A Multiplexed I-PDU holds no signal mappings of its own either, so its form has no PREVIEW tab and no SIGNALS table.

7.7.7 Signal (SIGNAL Tab)

A signal has the following editable fields.

Field	Form	Range and notes
Name	Text
Bit Length	Integer	1 or more, with no upper bound. A signal longer than 64 bits is exported as an ARRAY I-SIGNAL
Type	Choice	uint / sint / float / array / struct
Unit	Text
Factor	Decimal
Offset	Decimal
Min	Decimal
Max	Decimal
Signal Groups	Read-only	Lists the names of the groups the signal belongs to, joined by , . If it belongs to no group, - appears
Init Value	Value editor	See 7.11
Description	Text

The Signal Groups field is display only. To change group membership, edit the GROUP column in the SIGNALS table (see 7.9).

If the signal has Text Table (enumeration) entries, a section titled like Text Table (3 entries) is added below the form, and the entries are listed in the form Enumerator = Value. This section is read-only (see 7.12).

Type offers five options, whereas the TYPE column in the SIGNALS table offers only three: UINT, SINT, and FLOAT. You can set array and struct in this detail form only.

7.8 The PDU REFERENCES and FRAME REFERENCES Tabs

The references of a frame are edited on the second tab of the form's right column: PDU REFERENCES for a CAN frame and a LIN unconditional frame, FRAME REFERENCES for a LIN event-triggered or sporadic frame. Assign a reference as follows.

1. Click the tab. A picker appears at the right end of the tab bar; it shows the current references, or Select PDUs... / Select Frames... when there are none.
2. Click the picker. The candidate list opens as a check box dropdown. PDU candidates show their length and signal count as well, as in DoorStatus_FL_Pdu (8B, 3 sig); an N-PDU is listed as NewNPdu (8B, N-PDU).
3. Check the items you need. They are applied together when the dropdown closes.
4. The applied items appear in the table below the tab bar. With two or more items, a drag handle appears at the left of each row, and you can drag a row to reorder it.

The two tabs are structured as follows.

Tab	Picker text when empty	Table columns	Empty state
PDU REFERENCES	Select PDUs...	#, PDU Name, Length, Signals	No PDU assigned
FRAME REFERENCES	Select Frames...	#, Frame Name, ID, Length	No frame references. The candidates are the unconditional LIN frames, excluding the frame itself

Both references are required. Clearing every PDU reference is applied: the frame is left with no PDU, the table reads No PDU assigned, the picker is underlined in red, and the tab label turns red. A LIN event-triggered or sporadic frame with no frame reference is marked the same way. The tab carries the message (PDU References is required, Frame References is required) as its tooltip, so you can read it while PREVIEW is shown.

The PDU REFERENCES tab also reports layout errors. With PREVIEW shown, the label of the PDU REFERENCES tab turns red and its tooltip carries the message.

Situation	Message
The referenced PDU lengths add up to more than the frame's maximum size	Total PDU size 72B exceeds frame max size 64B
Signal bits overlap within one PDU	[DoorStatus_FL_Pdu] Signal "DoorLock_FL" overlaps with "WindowPos_FL" at bit 2

The maximum frame size is 64 bytes for CAN and 8 bytes for LIN.

7.9 The SIGNALS Table

The table appears below the form when you select a frame, an I-Signal I-PDU, or an NM-PDU. Its header reads SIGNALS, followed directly by the + button (tooltip Add Signal) that adds a signal. The header does not collapse. With no mappings at all, No signals. Click + to add a signal. appears.

The SIGNALS table — ① the + (Add Signal) after the title, ② the column header row, ③ the TYPE and BYTE-ORDER reference cells, ④ a PDU cell, ⑤ a GROUP cell being edited with its candidate list

Columns

The leading # column is the row number, and the last cell in each row holds a delete button (tooltip Remove Signal). Each column has the following editing form and constraints.

Column	Editing form	Where it is stored, and constraints
NAME	Text	The signal name. Sortable
TYPE	Reference cell (UINT / SINT / FLOAT)	Signal. The × clears the value (see below)
BYTE-ORDER	Reference cell (LITTLE-ENDIAN / BIG-ENDIAN)	Mapping. The × clears the value (see below)
GROUP	Autocomplete text	Signal group membership
START	Integer	Mapping. An integer, 0 or more. Sortable
LENGTH	Integer	Signal. An integer, 1 or more, with no upper bound. Sortable
UPDATE-BIT	Integer	Mapping. An integer, 0 or more. Clear it and the value is removed
FACTOR	Decimal	Signal. Fractions and negative values allowed
OFFSET	Decimal	Signal
MIN	Decimal	Signal
MAX	Decimal	Signal
UNIT	Text	Signal
INIT VALUE	Decimal, or a badge	See 7.11
PDU	Choice (no ×)	Moves the signal to another PDU. This column is hidden on the PDU tab, since there is nowhere to move it

• The TYPE and BYTE-ORDER cells each have an × and a chevron. Clicking the × empties the cell, and the empty cell is underlined in red as an error until you pick a value again.
• Drag the edge of a column header to change the width of that column only.
• Only three columns can be sorted: NAME, START, and LENGTH. Each click on the header cycles through no sort, ascending, descending, and no sort again.
• Rows whose signal bits overlap are highlighted.

Editing a Cell and Rejected Input

1. Click the cell. An input control opens in place. In a text cell, the caret is placed where you clicked.
2. Change the value and press Enter, or move the focus away. The value is committed.
3. Press Esc to cancel the edit and restore the original value.

Ctrl+S (save), Ctrl+Z (undo), and Ctrl+Shift+Z or Ctrl+Y (redo) work while you are editing. In that case the value under edit is committed first, and then the action runs. The GROUP column is the exception: it is an autocomplete editor, so it has no such immediate commit.

If the value matches what it was when editing started, nothing is committed. Opening a cell and closing it unchanged therefore does not mark the document dirty.

The following input is rejected.

Rejected input	Result and display
NAME is empty	Not saved; the tooltip Signal name cannot be empty appears
NAME violates the AUTOSAR rules	Not saved; the tooltip AUTOSAR naming convention: must start with a letter and contain only letters, digits, and underscores appears
NAME duplicates an existing signal	Not saved; the tooltip Signal name "Speed" already exists appears
START or UPDATE-BIT is negative or fractional	The edit is cancelled and the original value is restored
LENGTH is below 1 or fractional	The edit is cancelled and the original value is restored
A non-numeric value in a numeric column	The edit is cancelled and the original value is restored
GROUP violates the AUTOSAR rules	The edit is cancelled

Leading and trailing whitespace is trimmed from names before they are saved. Entering Speed saves Speed, for example.

GROUP Column Autocomplete

Click a GROUP cell and an input with the placeholder Group name... appears.

• The candidates are only the groups that signals in the current frame's PDUs actually belong to. This is not the project-wide group list. When no such group exists yet, no candidate list opens on the empty input.
• If no group matches the name you type, a Create "DoorStatus_FL_Grp" entry appears; choose it, or press Enter, to create the group and put the signal in it. On the next signal, the new group is offered as a candidate.
• Clear the value, or enter -, to remove the signal from its group.
• A signal belongs to one group at a time. Assigning a new group removes the existing membership first.

7.10 The PREVIEW Tab and the SIGNAL GROUPS Panel

The bit layout is shown in the PREVIEW tab of the form's right column; the signal group tree is the SIGNAL GROUPS panel on the right of the SIGNAL tab.

Bit Layout (PREVIEW Tab)

Shown for frames, and on the PDU tab for an I-Signal I-PDU or an NM-PDU. PREVIEW is the tab selected by default.

The PREVIEW tab — ① the bit number header row, ② a byte row label, ③ an MSB (M) marker, ④ the signal legend

• A bit number header row (7 6 5 4 3 2 1 0) comes first, followed by the byte rows in order: Byte 0, Byte 1, and so on.
• Each signal is assigned a color, and the legend on the right lists the signal names with their colors.
• The letter L marks each signal's LSB position and M marks its MSB position. The two positions swap with the byte order, and a 1-bit signal shows L only. A U marks the UPDATE-BIT position, and its tooltip reads Speed(UB).
• Overlapping bits are painted in the error color, and the tooltip names the overlapping signals, as in Overlap: Lock, Unlock. As soon as there is a single overlap, an Overlap (Error) entry is added to the legend.
• A frame longer than 16 bytes is drawn in a compact mode that omits the letters (no L, M, or U markers).
• On a frame that references several PDUs, the editor inserts the PDU name as a separator and draws the layouts one after another, PDU by PDU.

An overlap is not merely a display problem; it is an error you must fix. Find the overlapping position in the PREVIEW tab, then move the START value of one of the two signals so they no longer use the same bit (7.9). If there is still not enough room, check that the signal's last bit does not exceed the frame's DLC (Length for LIN) (7.7).

With an overlap present — ① the overlapping bit in the error color, ② the Overlap (Error) legend entry, ③ the PDU REFERENCES tab label in red (its tooltip gives the overlap message), ④ the overlapping rows highlighted in the SIGNALS table

Signal Group Tree (SIGNAL GROUPS Panel)

A read-only tree in the right-hand panel of the SIGNAL tab.

The SIGNAL tab — ① the read-only SIGNAL GROUPS field, ② INIT VALUE, ③ the SIGNAL GROUPS panel, ④ a group row with its signal count, expanded

• A group row shows the group name and the number of signals in it; click it to expand and collapse.
• Once expanded, click a signal name and the Configuration panel moves to that signal. If the name matches no signal in the dictionary — a dangling reference left by an import — the row does not respond to clicks.
• With no groups at all, No signal groups appears.

7.11 Initial Values (Init Value)

A signal's initial value is edited in the project-wide value editor (ValueSpecEditor). Because a signal references no data type, the input form is derived automatically from the signal's own properties.

Signal property	Input form
Has Text Table (enumeration) entries	A combo box. Entries appear in the form label = value
Bit length 1	A 0 or 1 numeric input (not a TRUE/FALSE toggle), labeled boolean (1-bit)
uint, n bits	An integer in the range 0 to 2^n-1
sint, n bits	An integer in the range -2^(n-1) to 2^(n-1)-1
float / array / struct	A number with no range limit

The behavior rules are as follows.

• The model always stores a number. Choosing an enumeration label stores that entry's numeric value.
• A value outside the range is still accepted; only an error marker appears. The editor neither clamps nor reverts the value. An imported model may hold out-of-range values, and changing them arbitrarily would corrupt the source.
• Imported struct, array, and map initial values are not editable; they appear in a read-only structure viewer.
• A true or false string initial value on a 1-bit signal is normalized to 1 or 0 on import, and the export writes only 0 or 1 (in the AUTOSAR rules, 1 ≡ true).

The INIT VALUE Column in the Table

• When the value is a plain number, the cell is editable as it stands. If the type is uint or sint, hovering over the cell shows a tooltip such as Derived range 0..255, and a value outside the range gets a warning marker on the cell (it is still saved). float, array, and struct have no range, so they get neither a tooltip nor a warning.
• When the value is structured, the cell becomes a badge that cannot be edited. The badge reads one of STRUCT, ARRAY, MAP, TEXT, APP, N/A, RULE, PRESERVED, or EXPR, and the tooltip gives a one-line summary such as record: 3 field(s).

The value editor shares its general rules with 09. Interface Editor.

7.12 Text Table (Enumeration)

The enumeration entries a signal holds are listed in the Text Table (N entries) section of the Configuration panel, in the form name = value.

Enumeration entries are read-only. They are created only by an ARXML or DBC import and cannot be changed in the editor.

7.13 Saving and Undo

The save and undo commands are as follows.

Action	Command	Notes
Save	Ctrl+S	Works while the focus is inside the editor, including while you edit a table cell
Undo	EDIT › Undo (Ctrl+Z)	The menu entry names the change, as in Undo Edit signals, DoorStatus_FL_Pdu
Redo	EDIT › Redo (Ctrl+Y; Ctrl+Shift+Z also works)

• On save, any input in progress — a text field awaiting commit, an open cell editor — is committed first and then the file is written, so a value is saved along with the rest even if you press Ctrl+S immediately after typing it.
• The keyboard shortcuts act while the focus is inside the editor. If the focus has left the editor, for example after a table edit has been committed, use EDIT › Undo.
• Undo brings the reverted element back into view: the editor switches to the tab that holds it and selects it. Undoing a START edit made in the table on the CAN tab, for example, switches to the PDU tab with that PDU selected, and undoing a table edit of a signal property switches to the SIGNAL tab.
• Undo uses a single timeline shared by the whole project. The EDIT menu in the header and Undo/Redo in the command palette use the same timeline (05. UI Layout and Navigation).
• With unsaved changes, a dirty marker appears next to the tab title, and closing the tab asks whether to save.

7.14 External Changes and Import

• When another program or another feature changes the Signal model, the file watcher detects it and the editor reloads the file.

• The automatic reload is skipped while there are unsaved changes or an edit is in progress. The following warning appears instead.

  Signal file changed on disk. Keeping your unsaved edits - save to overwrite the external change.

  This keeps an edit in progress from being silently overwritten, and lost, by the contents on disk. To continue, either save to overwrite the external change, or revert your edits and then reload.

• A project-wide ARXML or DBC import works differently. Before the import starts, the changes in every open editor are saved first, and when the import finishes this editor is reloaded unconditionally. Leaving a file the import overwrites unsaved would lose it on the reload.

7.15 Integration with Other Editors and Features

• System editor — the System editor edits the IVC model (design/IVC.io.model). The connector frame and PDU references in that model name the frames and PDUs defined here. Conversely, an N-PDU or a DCM-I-PDU created in the System editor's transport protocol configuration is added directly to this editor's live model and is recorded in the undo history, and gateway editing in the System editor can write signals into this model. The System editor's canvas opens this editor through its Signal icon (see the start of this chapter).

• System model data mappings — renaming a signal also updates the data mapping references in the System model (design/SYSTEM.io.model; signal-name, call-signal-name). The change is written to whichever open editor holds those mappings, or to the file on disk if none does. Either way it is grouped into the same undo step as the rename in the Signal editor.

• ECUC — this version does not generate module configurations such as Com and PduR from this model. Create them in the Module Configuration editor or import them (12. ECUC).

• Validation — the constraint check results for signals and PDUs are collected in the separate Validation panel (14. Validation). The Signal editor itself has no validation panel; it only paints the affected fields and tabs.

• DBC — you import a DBC file with the Import icon in the DESIGN header of the EDITOR view. This model is where the result lands.

  DBC export is not available in the current version (see 13. Import and Export).

7.16 Editing Rules Summary

• Names follow the AUTOSAR SHORT-NAME rules: the first character is a letter, and the rest are letters, digits, and underscores. The Name field in the Configuration panel does not apply a value to the model if it breaks these rules or is empty. A warning appears on screen and the previous name is kept. The rules also cap the length at 128 characters, but the editor does not enforce it, so a long name becomes a problem on ARXML export.
• Text input in the Configuration panel is committed when you stop typing or move the focus away. Hexadecimal identifier fields such as CAN ID apply a valid value immediately as you type, and revert to the previous value on focus loss if the value is out of range. Choices and toggles are committed immediately.
• Clearing Description does not store an empty string; it removes the description itself. The item — the frame, PDU, or signal — remains.
• Required references left empty — a frame's PDU references, the frame references of a LIN event-triggered or sporadic frame, and the I-PDU Ref of a Multiplexed I-PDU static part — are marked in red as errors. The TYPE and BYTE-ORDER of a signal mapping are required in the same way.
• Opening a field and closing it without changing the value does not mark the document dirty.
• The list sort and filter, the panel widths, the form height, the column widths, and the scroll positions are screen state only; they are not saved to the file.