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Timing Diagram

A Timing Diagram in UML is a specific type of interaction diagram that visualizes the timing constraints of a system. It focuses on the chronological order of events, showcasing how different objects interact with each other over time. Timing diagrams are especially useful in real-time systems and embedded systems to understand the behavior of objects throughout a given period.

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Declaring element or participant

You declare participant using the following keywords, depending on how you want them to be drawn.

Keyword	Description
analog	An analog signal is continuous, and the values are linearly interpolated between the given setpoints
binary	A binary signal restricted to only 2 states
clock	A clocked signal that repeatedly transitions from high to low, with a period, and an optional pulse and offset
concise	A simplified concise signal designed to show the movement of data (great for messages)
robust	A robust complex line signal designed to show the transition from one state to another (can have many states)

You define state change using the @ notation, and the is verb.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle @100 WU is Waiting WB is Processing @300 WB is Waiting @enduml

🎉 Copied!

@startuml clock "Clock_0" as C0 with period 50 clock "Clock_1" as C1 with period 50 pulse 15 offset 10 binary "Binary" as B concise "Concise" as C robust "Robust" as R analog "Analog" as A @0 C is Idle R is Idle A is 0 @100 B is high C is Waiting R is Processing A is 3 @300 R is Waiting A is 1 @enduml

[Ref. QA-14631, QA-14647 and QA-11288]

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Binary and Clock

It's also possible to have binary and clock signal, using the following keywords:

• binary
• clock

🎉 Copied!

@startuml clock clk with period 1 binary "Enable" as EN @0 EN is low @5 EN is high @10 EN is low @enduml

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Adding message

You can add message using the following syntax.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle @100 WU -> WB : URL WU is Waiting WB is Processing @300 WB is Waiting @enduml

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Relative time

It is possible to use relative time with @.

🎉 Copied!

@startuml robust "DNS Resolver" as DNS robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle DNS is Idle @+100 WU -> WB : URL WU is Waiting WB is Processing @+200 WB is Waiting WB -> DNS@+50 : Resolve URL @+100 DNS is Processing @+300 DNS is Idle @enduml

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Anchor Points

Instead of using absolute or relative time on an absolute time you can define a time as an anchor point by using the as keyword and starting the name with a :.

@XX as :<anchor point name>

🎉 Copied!

@startuml clock clk with period 1 binary "enable" as EN concise "dataBus" as db @0 as :start @5 as :en_high @10 as :en_low @:en_high-2 as :en_highMinus2 @:start EN is low db is "0x0000" @:en_high EN is high @:en_low EN is low @:en_highMinus2 db is "0xf23a" @:en_high+6 db is "0x0000" @enduml

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Participant oriented

Rather than declare the diagram in chronological order, you can define it by participant.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @WB 0 is idle +200 is Proc. +100 is Waiting @WU 0 is Waiting +500 is ok @enduml

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Setting scale

You can also set a specific scale.

🎉 Copied!

@startuml concise "Web User" as WU scale 100 as 50 pixels @WU 0 is Waiting +500 is ok @enduml

When using absolute Times/Dates, 1 "tick" is equivalent to 1 second.

🎉 Copied!

@startuml concise "Season" as S '30 days is scaled to 50 pixels scale 2592000 as 50 pixels @2000/11/01 S is "Winter" @2001/02/01 S is "Spring" @2001/05/01 S is "Summer" @2001/08/01 S is "Fall" @enduml

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Initial state

You can also define an inital state.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU WB is Initializing WU is Absent @WB 0 is idle +200 is Processing +100 is Waiting @WU 0 is Waiting +500 is ok @enduml

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Intricated state

A signal could be in some undefined state.

Intricated or undefined robust state

🎉 Copied!

@startuml robust "Signal1" as S1 robust "Signal2" as S2 S1 has 0,1,2,hello S2 has 0,1,2 @0 S1 is 0 S2 is 0 @100 S1 is {0,1} #SlateGrey S2 is {0,1} @200 S1 is 1 S2 is 0 @300 S1 is hello S2 is {0,2} @enduml

Intricated or undefined binary state

🎉 Copied!

@startuml clock "Clock" as C with period 2 binary "Enable" as EN @0 EN is low @1 EN is high @3 EN is low @5 EN is {low,high} @10 EN is low @enduml

[Ref. QA-11936 and QA-15933]

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Hidden state

It is also possible to hide some state.

🎉 Copied!

@startuml concise "Web User" as WU @0 WU is {-} @100 WU is A1 @200 WU is {-} @300 WU is {hidden} @400 WU is A3 @500 WU is {-} @enduml

🎉 Copied!

@startuml scale 1 as 50 pixels concise state0 concise substate1 robust bit2 bit2 has HIGH,LOW @state0 0 is 18_start 6 is s_dPause 8 is 10_data 14 is {hidden} @substate1 0 is sSeq 4 is sPause 6 is {hidden} 8 is dSeq 12 is dPause 14 is {hidden} @bit2 0 is HIGH 2 is LOW 4 is {hidden} 8 is HIGH 10 is LOW 12 is {hidden} @enduml

[Ref. QA-12222]

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Hide time axis

It is possible to hide time axis.

🎉 Copied!

@startuml hide time-axis concise "Web User" as WU WU is Absent @WU 0 is Waiting +500 is ok @enduml

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Using Time and Date

It is possible to use time or date.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @2019/07/02 WU is Idle WB is Idle @2019/07/04 WU is Waiting : some note WB is Processing : some other note @2019/07/05 WB is Waiting @enduml

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @1:15:00 WU is Idle WB is Idle @1:16:30 WU is Waiting : some note WB is Processing : some other note @1:17:30 WB is Waiting @enduml

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Adding constraint

It is possible to display time constraints on the diagrams.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU WB is Initializing WU is Absent @WB 0 is idle +200 is Processing +100 is Waiting WB@0 <-> @50 : {50 ms lag} @WU 0 is Waiting +500 is ok @200 <-> @+150 : {150 ms} @enduml

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Highlighted period

You can higlight a part of diagram.

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle @100 WU -> WB : URL WU is Waiting #LightCyan;line:Aqua @200 WB is Proc. @300 WU -> WB@350 : URL2 WB is Waiting @+200 WU is ok @+200 WB is Idle highlight 200 to 450 #Gold;line:DimGrey : This is my caption highlight 600 to 700 : This is another\nhighlight @enduml

[Ref. QA-10868]

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Using notes

You can use the note top of and note bottom of keywords to define notes related to a single object or participant (available only for concise or binary object).

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle @100 WU is Waiting WB is Processing note top of WU : first note\non several\nlines note bottom of WU : second note\non several\nlines @300 WB is Waiting @enduml

[Ref. QA-6877, GH-1465]

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Adding texts

You can optionally add a title, a header, a footer, a legend and a caption:

🎉 Copied!

@startuml Title This is my title header: some header footer: some footer legend Some legend end legend caption some caption robust "Web Browser" as WB concise "Web User" as WU @0 WU is Idle WB is Idle @100 WU is Waiting WB is Processing @300 WB is Waiting @enduml

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Complete example

Thanks to Adam Rosien for this example.

🎉 Copied!

@startuml concise "Client" as Client concise "Server" as Server concise "Response freshness" as Cache Server is idle Client is idle @Client 0 is send Client -> Server@+25 : GET +25 is await +75 is recv +25 is idle +25 is send Client -> Server@+25 : GET\nIf-Modified-Since: 150 +25 is await +50 is recv +25 is idle @100 <-> @275 : no need to re-request from server @Server 25 is recv +25 is work +25 is send Server -> Client@+25 : 200 OK\nExpires: 275 +25 is idle +75 is recv +25 is send Server -> Client@+25 : 304 Not Modified +25 is idle @Cache 75 is fresh +200 is stale @enduml

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Digital Example

🎉 Copied!

@startuml scale 5 as 150 pixels clock clk with period 1 binary "enable" as en binary "R/W" as rw binary "data Valid" as dv concise "dataBus" as db concise "address bus" as addr @6 as :write_beg @10 as :write_end @15 as :read_beg @19 as :read_end @0 en is low db is "0x0" addr is "0x03f" rw is low dv is 0 @:write_beg-3 en is high @:write_beg-2 db is "0xDEADBEEF" @:write_beg-1 dv is 1 @:write_beg rw is high @:write_end rw is low dv is low @:write_end+1 rw is low db is "0x0" addr is "0x23" @12 dv is high @13 db is "0xFFFF" @20 en is low dv is low @21 db is "0x0" highlight :write_beg to :write_end #Gold:Write highlight :read_beg to :read_end #lightBlue:Read db@:write_beg-1 <-> @:write_end : setup time db@:write_beg-1 -> addr@:write_end+1 : hold @enduml

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Adding color

You can add color.

🎉 Copied!

@startuml concise "LR" as LR concise "ST" as ST LR is AtPlace #palegreen ST is AtLoad #gray @LR 0 is Lowering 100 is Lowered #pink 350 is Releasing @ST 200 is Moving @enduml

[Ref. QA-5776]

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Using (global) style

Without style (by default)

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU WB is Initializing WU is Absent @WB 0 is idle +200 is Processing +100 is Waiting WB@0 <-> @50 : {50 ms lag} @WU 0 is Waiting +500 is ok @200 <-> @+150 : {150 ms} @enduml

With style

You can use style to change rendering of elements.

🎉 Copied!

@startuml <style> timingDiagram { document { BackGroundColor SandyBrown } constraintArrow { LineStyle 2-1 LineThickness 3 LineColor Blue } } </style> robust "Web Browser" as WB concise "Web User" as WU WB is Initializing WU is Absent @WB 0 is idle +200 is Processing +100 is Waiting WB@0 <-> @50 : {50 ms lag} @WU 0 is Waiting +500 is ok @200 <-> @+150 : {150 ms} @enduml

[Ref. QA-14340]

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Applying Colors to specific lines

You can use the <style> tags and sterotyping to give a name to line attributes.

🎉 Copied!

@startuml <style> timingDiagram { .red { LineColor red } .blue { LineColor blue LineThickness 5 } } </style> clock clk with period 1 binary "Input Signal 1" as IS1 binary "Input Signal 2" as IS2 <<blue>> binary "Output Signal 1" as OS1 <<red>> @0 IS1 is low IS2 is high OS1 is low @2 OS1 is high @4 OS1 is low @5 IS1 is high OS1 is high @6 IS2 is low @10 IS1 is low OS1 is low @enduml

[Ref. QA-15870]

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Compact mode

You can use compact command to compact the timing layout.

By default

🎉 Copied!

@startuml robust "Web Browser" as WB concise "Web User" as WU robust "Web Browser2" as WB2 @0 WU is Waiting WB is Idle WB2 is Idle @200 WB is Proc. @300 WB is Waiting WB2 is Waiting @500 WU is ok @700 WB is Idle @enduml

Global mode with mode compact

🎉 Copied!

@startuml mode compact robust "Web Browser" as WB concise "Web User" as WU robust "Web Browser2" as WB2 @0 WU is Waiting WB is Idle WB2 is Idle @200 WB is Proc. @300 WB is Waiting WB2 is Waiting @500 WU is ok @700 WB is Idle @enduml

Local mode with only compact on element

🎉 Copied!

@startuml compact robust "Web Browser" as WB compact concise "Web User" as WU robust "Web Browser2" as WB2 @0 WU is Waiting WB is Idle WB2 is Idle @200 WB is Proc. @300 WB is Waiting WB2 is Waiting @500 WU is ok @700 WB is Idle @enduml

[Ref. QA-11130]

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Scaling analog signal

You can scale analog signal.

Without scaling: 0-max (by default)

🎉 Copied!

@startuml title Between 0-max (by default) analog "Analog" as A @0 A is 350 @100 A is 450 @300 A is 350 @enduml

With scaling: min-max

🎉 Copied!

@startuml title Between min-max analog "Analog" between 350 and 450 as A @0 A is 350 @100 A is 450 @300 A is 350 @enduml

[Ref. QA-17161]

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Customise analog signal

Without any customisation (by default)

🎉 Copied!

@startuml analog "Vcore" as VDD analog "VCC" as VCC @0 VDD is 0 VCC is 3 @2 VDD is 0 @3 VDD is 6 VCC is 6 VDD@1 -> VCC@2 : "test" @enduml

With customisation (on scale, ticks and height)

🎉 Copied!

@startuml analog "Vcore" as VDD analog "VCC" between -4.5 and 6.5 as VCC VCC ticks num on multiple 3 VCC is 200 pixels height @0 VDD is 0 VCC is 3 @2 VDD is 0 @3 VDD is 6 VCC is 6 VDD@1 -> VCC@2 : "test" @enduml

[Ref. QA-11288]

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Order state of robust signal

Without order (by default)

🎉 Copied!

@startuml robust "Flow rate" as rate @0 rate is high @5 rate is none @6 rate is low @enduml

With order

🎉 Copied!

@startuml robust "Flow rate" as rate rate has high,low,none @0 rate is high @5 rate is none @6 rate is low @enduml

With order and label

🎉 Copied!

@startuml robust "Flow rate" as rate rate has "35 gpm" as high rate has "15 gpm" as low rate has "0 gpm" as none @0 rate is high @5 rate is none @6 rate is low @enduml

[Ref. QA-6651]