diff --git a/src/central-execution-engine-spec.adoc b/src/central-execution-engine-spec.adoc
index 061e04c..2d2b6cc 100644
--- a/src/central-execution-engine-spec.adoc
+++ b/src/central-execution-engine-spec.adoc
@@ -11,4 +11,5 @@ include::execution-engine-spec/intro.adoc[]
 include::execution-engine-spec/program-and-exception-status-registers.adoc[]
 include::execution-engine-spec/channel-io-overview.adoc[]
 include::execution-engine-spec/instructions.adoc[]
-include::execution-engine-spec/subsystems.adoc[]
\ No newline at end of file
+include::execution-engine-spec/subsystems.adoc[]
+include::execution-engine-spec/system-behavior.adoc[]
\ No newline at end of file
diff --git a/src/execution-engine-spec/instructions.adoc b/src/execution-engine-spec/instructions.adoc
index 1fc8211..3bf6b3f 100644
--- a/src/execution-engine-spec/instructions.adoc
+++ b/src/execution-engine-spec/instructions.adoc
@@ -491,7 +491,7 @@ ssr ss15, pc, sr32, 0 <2>
 
 Privileged instruction:: No. (The access control is done at the register/command level).
 Updates program state flags:: No.
-Exceptions:: UnknownInstr.
+Exceptions:: PrivFault.
 
 <<<
 ===== SSW: Subsystem Register Write
@@ -539,5 +539,5 @@ ssw ss15, pc, sr32, 0 <2>
 
 Privileged instruction:: No. (The access control is done at the register/command level).
 Updates program state flags:: No.
-Exceptions:: UnknownInstr.
+Exceptions:: PrivFault.
 
diff --git a/src/execution-engine-spec/intro.adoc b/src/execution-engine-spec/intro.adoc
index 6f5ab4c..e07271d 100644
--- a/src/execution-engine-spec/intro.adoc
+++ b/src/execution-engine-spec/intro.adoc
@@ -88,6 +88,9 @@ Debug::
 SvcDebug::
     This exception is the same as the *Debug* exception, except it is generated when debug events are encountered while in supervisor-mode.
 
+PrivFault::
+    This exception is generated when unprivileged software tries to execute a privileged instruction or tries to acces a privileged susbsystem register.
+
 UnknownInstr::
     This exception is generated when an unknown instruction failed to be executed.
     It is important not to ignore this exception as it can be the symptom of a memory corruption bug.
diff --git a/src/execution-engine-spec/program-and-exception-status-registers.adoc b/src/execution-engine-spec/program-and-exception-status-registers.adoc
index d6f3aee..c3f431c 100644
--- a/src/execution-engine-spec/program-and-exception-status-registers.adoc
+++ b/src/execution-engine-spec/program-and-exception-status-registers.adoc
@@ -17,7 +17,7 @@
 ], config: {label: {right: 'psr'}}}
 ....
 
-Only the ALU flags (C, Z, N, V) can be written to. Writing a 32-bits value into *psr* thus ignores the 28 upper bits.
+Only the ALU flags (C, Z, N, V) can be written to. Writing a 32-bits value into *psr* thus ignores the 28 upper bits in any system mode.
 
 === Exception Status Registers
 
@@ -37,3 +37,49 @@ Only the ALU flags (C, Z, N, V) can be written to. Writing a 32-bits value into
 ], config: {label: {right: 'esr_fault'}}}
 ....
 
+.Exceptions
+[%header,cols="1,1,3"]
+|===
+|Value |Name |Argument
+
+|0
+|_Reset_
+|_N/A_
+
+|1
+|SVC
+|The SVC number.
+
+|2
+|MemFault
+|The virtual address being accessed.
+
+|3
+|SysTick
+|_N/A_
+
+|4
+|Debug
+|#TODO: Describe it.#
+
+|5
+|SvcDebug
+|#TODO: Describe it.#
+
+|6
+|PrivFault
+|#TODO Describe it.#
+
+|7
+|UnknownInstr
+|The virtual address of the instruction.
+
+|8
+|HdwrMgmt
+|#TODO Describe it.#
+
+|9
+|Channel
+|The channel number and exception reason. #TODO: Describe it.#
+|===
+
diff --git a/src/execution-engine-spec/system-behavior.adoc b/src/execution-engine-spec/system-behavior.adoc
new file mode 100644
index 0000000..323f7e7
--- /dev/null
+++ b/src/execution-engine-spec/system-behavior.adoc
@@ -0,0 +1,35 @@
+== System Behavior
+=== On Reset
+
+On reset, the _Execution Engine_ assumes that the bootloader software was loaded in memory at address 0x0000_0000. +
+The _Execution Engine_ starts execution in Supervisor mode.
+
+.Registers content on reset
+[cols="1,2,3"]
+|===
+|Register |Value |Description
+
+|r0
+|_Execution Engine_ ID
+|Contains the execution engine ID. Reserved for when multiple _Execution Engines_ in a _Processing Unit_ will be specified. Always 0 until then.
+
+|r1..r7, lr, sp_user, sp_svc, sp_fault
+|_Unspecified_
+|N/A
+
+|pc_user, pc_fault
+|0x0000_0004
+|#TODO: Describe it#
+
+|pc_svc
+|0x0000_0000
+|#TODO: Describe it#
+
+|psr
+|_See description_
+|U=0, S=1, F=0. C, Z, N and V are undefined.
+
+|esr_svc, esr_fault
+|0x0000_0000
+|exc=_Reset_
+|===