Binary Arithmetic Device-16 (BAD16) Specification
            -------------------------------------------------

    1. Technical Summary

* 16-bit words
* Four general purpose registers
* Based on a really weird dream I had this one time.


    2. Registers

All general-purpose registers (R0-R3) are addresable as one 16-bit word (Rn),
or as two 8-bit words (RHn for the high half, and RLn for the low half).
Index registers are addressable as one 16-bit word only.

General Purpose
    * R0 (16-bit), RH0/RL0 (8-bit)
    * R1 (16-bit), RH1/RL1 (8-bit)
    * R2 (16-bit), RH2/RL2 (8-bit)
    * R3 (16-bit), RH3/RL3 (8-bit)

Index Registers (16-bit)
    * SP: Stack pointer
    * DP: Data pointer
    * IR: Interrupt address register
    * PC: Program counter

Flags (8-bit)
    * PSR: Processor Status Register
    * FSR: Floating-point Status Register

    3. Addressing Modes

The notation [VALUE] refers to the memory location at address [VALUE].

The following addressing modes are supported:

    4. Opcodes

Opcodes are one to three words in length, and are uniquely identified by the
first word.
+----------------------------------------------------------------------------+
| Cycles | Value     | Description
+--------+-----------+-------------------------------------------------------+
| 0      | 0x00-0x07 | 16-bit register (R0 - R3, SP, DP, IR, PC)
| 0      | 0x08-0x0c | 8-bit register low (RL0-RL3)
| 0      | 0x0d-0x10 | 8-bit register high (RH0-RH3)
| 0      | 0x11-0x19 | Register indirect: [16-bit register]
| 1      | 0x20      | Frame-local with offset: [SP + PC++]
| 1      | 0x21      | Frame-local with immediate offset: [SP + u16(PC++) ]
| 1      | 0x22      | Global with offset: [DP + value(PC++)]
| 1      | 0x23      | Global with immediate offset: [DP + u16(PC++) ]

    5. Memory Management

The BADCPU-16 address bus is 24 bits wide, allowing an address space of up to 16
megabytes. When paging is not enabled, the 8 most significant bits of the
address bus are always set to 0, restricting the address space to 64 kilobytes.

When paging is enabled, physical addresses are formed by concatenating