# Cardiograph issues

## Open

### #4 - Add single stepping

Q: should this be part of a more complex monitor interface? See note from [2023-08-31](../2023-08-31.md#microprocessor-trainer-style-keypad)

Or, a simpler option would be to add a command line flag:

    -s --singlestep

(Adapted from [#1](#1---improve-cli-interface))

### #3 - Add plain-text display output

With a command line option on `cardiograph.js`:

    -p, --prettydisplay

(Adapted from [#1](#1---improve-cli-interface))

### #2 - Startup: Execute `JMP $FF`

See [2023-08-24](../notes/2023-08-24.md#cpu-start-up)

... say that there's a 1-byte ROM at $FF.

- `00-19` - display (5x5)
- `1A   ` - pointer to display memory
- `1B   ` - keypad: value of latest key pressed
- `1C   ` - reserved for future use (bank switching flag)
- `1D   ` - initial IP
- `1D-FE` - free
- `FF   ` - ROM (unwriteable) - pointer to initial IP

- store `$1D` at `$FF`
- make CPU execute `JMP $FF` on startup
- make ROM unwriteable

More step-by-step:

  - Change memory from a Uint8Array to a regular array,
    and make every entry { number | { type: 'ROM', value: number }}
  - Store ROM as an object in machine.config.js
  - Load ROM data into memory at CPU startup (`startCPU(RAM, ROM)`)


## Closed

### #1 - Improve CLI interface

I'm thinking of an interface like this...

    $ ./cpu.js -mc code.bin  
    $ ./cpu.js code.asm
    $ ./cpu.js --debug code.asm

Full list of flags I want:

    -d --debug
    -s --singlestep
    -p --prettydisplay
    -mc --machinecode