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Change specification

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Changes:
- ADC was moved to a small opcode (D)
- LDVR was renamed to LDRS and moved to FA
- STVR was renamed to STRS and moved to FB
- LDRF (FC) and STRF (FD) were added
- Slightly altered document structure
- Added TOC
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Joscha 2019-11-10 16:55:54 +00:00
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README.md
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# mima-tools
## MiMa specification
* [Specification](#specification)
* [Instructions](#instructions)
* [Registers](#registers)
* [Opcodes](#opcodes)
* [Memory dump file format: `.mima`](#memory-dump-file-format-mima)
* [Programs](#programs)
### General
## Specification
In the following sections, `<a>` means "the value at the address
`a`". In the case of `<<a>>`, bits 19-0 of `<a>` are interpreted as
@ -63,7 +68,7 @@ ignored. They don't have to be set to 0.
### Opcodes
| Opcode | Name | Function |
|--------|---------------------------------------------|--------------------------------|
|--------|---------------------------------|--------------------------------|
| `0` | `LDC c` (load constant) | `c -> ACC` |
| `1` | `LDV a` (load value) | `<a> -> ACC` |
| `2` | `STV a` (store value) | `ACC -> <a>` |
@ -77,8 +82,7 @@ ignored. They don't have to be set to 0.
| `A` | `LDIV a` (load indirect value) | `<<a>> -> ACC` |
| `B` | `STIV a` (store indirect value) | `ACC -> <<a>>` |
| `C` | `CALL a` | `IAR -> RA; JMP a` |
| `D` | `LDVR d` (load value with relative offset) | `<SP + d> -> ACC` |
| `E` | `STVR d` (store value with relative offset) | `ACC -> <SP + d>` |
| `D` | `ADC c` (add constant) | `ACC + c -> ACC` |
| `F0` | `HALT` | Halt execution |
| `F1` | `NOT` | `not ACC -> ACC` |
| `F2` | `RAR` (rotate ACC right) | `ACC >> 1 -> ACC` |
@ -89,18 +93,27 @@ ignored. They don't have to be set to 0.
| `F7` | `STSP` (store to SP) | `ACC -> SP` |
| `F8` | `LDFP` (load from FP) | `FP -> ACC` |
| `F9` | `STFP` (store to FP) | `ACC -> FP` |
| `FA` | `ADC c` (add constant) | `ACC + c -> ACC` |
| `FA` | `LDRS o` (load relative to SP) | `<SP + o> -> ACC` |
| `FB` | `STRS o` (store relative to SP) | `ACC -> <SP + o>` |
| `FC` | `LDRF o` (load relative to FP) | `<FP + o> -> ACC` |
| `FD` | `STRF o` (store relative to FP) | `ACC -> <FP + o>` |
* `LDC c` sets bits 23-20 of `ACC` to 0.
* `ADD a`, `AND a`, `OR a`, `XOR a` and `NOT` are bitwise operations
* `RAR` shifts all bits in the `ACC` right by one. The rightmost bit wraps around to the leftmost position.
* `ADC c` interprets bits 15-0 as a signed integer, whose value is then added to the `ACC`'s current value.
* `ADC c` interprets its 20-bit value as a signed integer, whose value
is then added to the `ACC`'s current value.
* `RAR` shifts all bits in the `ACC` right by one. The rightmost bit
wraps around to the leftmost position.
* `LDRS`, `STRS`, `LDRF` and `STRF` interpret their 16-bit value as a
signed integer, whose value is then added to the address in the
respective register.
## File format
## Memory dump file format: `.mima`
All tools share a common file format with extension `.mima`. It
contains the whole execution state of a MiMa, meaning the contents of
its memory and all its registers.
All tools share a common memory dump file format with extension
`.mima`. It contains the whole execution state of a MiMa, meaning the
contents of its memory and all its registers. It also doubles as "MiMa
excutable" format.
The file is split up into blocks of 3 bytes, which form MiMa
words. The bytes within a word are ordered from most to least
@ -119,7 +132,7 @@ with zeroes, like so:
The registers and memory are stored as follows:
| Word | Content |
|--------------:|-------------|
|--------------:|:------------|
| 0 | `IAR` |
| 1 | `ACC` |
| 2 | `RA` |