Added more informations on LC-2 interrupts and startup

content/isa-docs/lc-2/_index.md

@@ -98,11 +98,25 @@ implicitly read by conditional branch instructions.
 
   [^lc2-condition-codes]: {{< cite-ics edition="1" chapter="5.1.7 Condition Codes" page="95" >}}
 
+## Startup Behavior
+
+The ISA does not specify a default starting address or reset vector. Where the
+PC is initialized when the processor powers on or resets is left entirely to
+the implementation. {{< citation-needed >}}
+
 ## Interrupt Support
 
-LC-2 provides basic support for interrupts via the `RTI` (Return from
+LC-2 provides support for vectored interrupts. When an interrupt is serviced,
-Interrupt) instruction. When an interrupt is serviced, the processor saves the
+the processor pushes the current PC and CC onto the stack, then reads an 8-bit
-current status onto the stack and jumps to the interrupt handler. `RTI`
+value from the interrupting device, called the interrupt vector (`INTV`).
-restores the PC from the stack when the handler returns. The ISA does not
+`INTV` is zero-extended to 16 bits and used as a memory address into the
-specify the interrupt protocol, the bus signaling, or the acknowledgment
+interrupt table: the value stored at that address is loaded into the PC,
-mechanism. These details are left to the implementation.
+transferring control to the interrupt handler.{{< citation-needed >}}
+
+The `RTI` (Return from Interrupt) instruction reverses this process, popping
+the PC and CC from the stack to resume the interrupted
+program.{{< citation-needed >}}
+
+Beyond this, the ISA does not specify the interrupt protocol in further detail:
+the bus signaling and acknowledgment mechanism used to deliver `INTV` are left
+to the implementation.

content/isa-docs/lc-2/memory.md

@@ -24,12 +24,12 @@ system, not the ISA itself. The ISA only defines the trap vector table at
 `0x0000 - 0x00FF`. Everything else, from the location of the OS to the boundary
 of userspace, is a software convention rather than a hardware requirement.
 
-| Range               | Purpose                               |
+| Range               | Purpose                                                                       |
-|:-------------------:|:-------------------------------------:|
+|:-------------------:|:-----------------------------------------------------------------------------:|
-| `0x0000` - `0x00FF` | Trap Vector Table[^lc2-trap]          |
+| `0x0000` - `0x00FF` | Trap Vector Table[^lc2-trap] / [Interrupt Vector Table](..#interrupt-support) |
-| `0x0100` - `0x2FFF` | Operating System[^matt-postiff-guide] |
+| `0x0100` - `0x2FFF` | Operating System[^matt-postiff-guide]                                         |
-| `0x3000` - `0xCFFF` | Userspace                             |
+| `0x3000` - `0xCFFF` | Userspace                                                                     |
-| `0xD000` - `0xFFFF` | Device Registers                      |
+| `0xD000` - `0xFFFF` | Device Registers                                                              |
 
 [^lc2-trap]: {{< cite-ics edition="1" chapter="Appendix A.3 The Instruction Set" page="448" page-end="449" >}}
 [^matt-postiff-guide]: {{< cite-web