| 0200 | 89 | BUF | BASIC Line Editor Input Buffer | |
| 0259 | | | Kernal File Tables | |
| 0259 | 10 | LAT | Active logical file number table | |
| 0263 | 10 | FAT | Device number for each logical file | |
| 026D | 10 | SAT | Secondary address for each logical file | |
| 0277 | 10 | KEYD | Keyboard buffer | |
| 0281 | 2 | MEMSTR | Start of Memory pointer | 0x0800 |
| 0283 | 2 | MEMSIZ | End of Memory pointer Usually this is the first byte of the BASIC ROM | 0xA000 |
| 0286 | | | Screen workspace | |
| 0286 | 1 | COLOR | Current Foreground text colour | |
| 0287 | 1 | GDCOL | Colour of character under Cursor | |
| 0288 | 1 | HIBASE | Page of Screen Memory | 0x04 |
| 0289 | | | Keyboard workspace | |
| 0289 | 1 | XMAX | Max length of keyboard buffer
| 0x00 |
No buffer |
| 0x01-0x0F |
Buffer size |
| |
| 028A | 1 | RPTFLG | Which keys will repeat
| 0x00 |
Only cursor, insert, delete or space repeat |
| 0x40 |
No keys repeat |
| 0x80 |
All keys repeat |
| |
| 028D | 1 | SHFLAG | Shift/Ctrl/Commodore key pressed
| Bit 0 |
1=Left or Right shift is pressed or Shift Lock is active |
| Bit 1 |
1=Commodore key pressed |
| Bit 2 |
1=Control pressed |
| |
| 028E | 1 | LSTSHF | Last value of Shift/Ctrl/Commodore key pressed Used with SHFLAG to debounce those keys. Values match those for SHFLAG | |
| 0291 | 1 | MODE | Shift/Commodore switch Enables/Disables character switching when Shift & Commodore keys are pressed
| 0x00 |
Commodore-Shift is disabled |
| 0x80 |
Commodore-Shift will toggle between uppercase/graphics & lowercase/uppercase character set |
| |
| 0292 | 1 | AUTODN | Screen scrolling enabled 0 enables scrolling, any other value disables scrolling | |
| 0293 | | | Mock 6551 RS-232 | |
| 0293 | 1 | M51CTR | Mock 6551 RS-232 Control Register
| %0xxxxxxx |
1 stop bit |
| %1xxxxxxx |
2 stop bits |
| %x00xxxxx |
8 data bits |
| %x01xxxxx |
7 data bits |
| %x10xxxxx |
6 data bits |
| %x11xxxxx |
5 data bits |
| %xxxx0110 |
300 bps |
| %xxxx1000 |
1200 bps |
| %xxxx1010 |
2400 bps |
| |
| 0294 | 1 | M51CDR | Mock 6551 RS-232 Command Register
| %001xxxxx |
Odd Parity |
| %011xxxxx |
Even Parity |
| %101xxxxx |
Mark Parity |
| %111xxxxx |
Space Parity |
| %xx0xxxxx |
No parity |
| %xxx0xxxx |
Full Duplex |
| %xxx1xxxx |
Half Duplex |
| %xxxxxxx0 |
3 Line |
| %xxxxxxx1 |
X Line |
| |
| 0295 | 2 | M51AJB | Mock 6551 RS-232 Nonstandard Bit Timing Not actually used by Kernal but present for 6551 UART emulation | |
| 0297 | 1 | M51STAT | Mock 6551 RS-232 Status Register
| Bit 0 |
1=Parity Error |
| Bit 1 |
1=Framing Error |
| Bit 2 |
1=Receive Buffer Overrun |
| Bit 3 |
1=Receive Buffer Empty |
| Bit 4 |
1=CTS (Clear To Send) Signal Missing |
| Bit 5 |
Unused |
| Bit 6 |
1=DTR (Data Set Ready) Signal Missing |
| Bit 7 |
1=Break Detected |
| |
| 0298 | 3 | | Used by Kernal for RS-232 | |
| 029B | | | RS-232 Buffers | |
| 029B | 1 | RIDBE | RS-232 Index to end of receive buffer | |
| 029C | 1 | RIDBS | RS-232 Index to start of receive buffer | |
| 029D | 1 | RODBE | RS-232 Index to end of transmit buffer | |
| 029E | 1 | RODBS | RS-232 Index to start of transmit buffer | |
| 02A1 | 1 | ENABL | RS-232 Interrupts Enabled
| Bit 0 |
System is transmitting data |
| Bit 1 |
System is receiving data |
| Bit 4 |
System is waiting for receiver edge |
| |
| 02A2 | | | Used by Kernal | |
| 02A7 | 89 | | Unused, available for application use | |