Kernal
Commodore's low-level Operating System was named the Kernal. It comprises the set of low-level hardware interfaces which is consequently used throughout Commodore's 8-bit computer series, beginning with the Commodore PET.
In the 1980's many people believed the word KERNAL was an abbreviation for "Keyboard Entry Read, Network, And Link". According to the legendary account from Robert Russell —one of the dominant people around the development of the VIC20— this name had its origin from a mistake Russell made during the creation of the VIC 20 Programmer's Guide[1] This spelling has been repeated thereafter in countless publications and in the documentation for succeeding machines like the C64[2] or C128.[3]
Functions[edit | edit source]
The Kernal consisted of thirty-nine (39) functions ranging from Input/Output control to file management, memory management, console management and time management. These functions formed the basis for higher level routines in the BASIC ROM like LOAD, SAVE, INPUT and PRINT.
Kernal functions are accessible via a jump-table at the end of addressable memory ($FF81-$FFF3). The Kernal ROM occupied the last 8KB of address space in Commodore 8-bit computers ($E000-$FFFF).
| Name | Address | Function | |
| Hexadecimal | Decimal | ||
| ACPTR | $FFA5 | 65445 | Input byte from serial port |
| CHKIN | $FFC6 | 65478 | Open channel for input |
| CHKOUT | $FFC9 | 65481 | Open a channel for output |
| CHRIN | $FFCF | 65487 | Get a character from the input channel |
| CHROUT | $FFD2 | 65490 | Output a character |
| CIOUT | $FFA8 | 65448 | Transmit a byte over the serial bus |
| CINT | $FF81 | 65409 | Initialize the screen editor and VIC-II Chip |
| CLALL | $FFE7 | 65511 | Close all open files |
| CLOSE | $FFC3 | 65475 | Close a logical file |
| CLRCHN | $FFCC | 65484 | Clear all I/O channels |
| GETIN | $FFE4 | 65508 | Get a character |
| IOBASE | $FFF3 | 65523 | Define I/O memory page |
| IOINIT | $FF84 | 65412 | Initialize I/O devices |
| LISTEN | $FFB1 | 65457 | Command a device on the serial bus to listen |
| LOAD | $FFD5 | 65493 | Load RAM from device |
| MEMBOT | $FF9C | 65436 | Set bottom of memory |
| MEMTOP | $FF99 | 65433 | Set the top of RAM |
| OPEN | $FFC0 | 65472 | Open a logical file |
| PLOT | $FFF0 | 65520 | Set or retrieve cursor location |
| RAMTAS | $FF87 | 65415 | Perform RAM test |
| RDTIM | $FFDE | 65502 | Read system clock |
| READST | $FFB7 | 65463 | Read status word |
| RESTOR | $FF8A | 65418 | Set the top of RAM |
| SAVE | $FFD8 | 65496 | Save memory to a device |
| SCNKEY | $FF9F | 65439 | Scan the keyboard |
| SCREEN | $FFED | 65517 | Return screen format |
| SECOND | $FF93 | 65427 | Send secondary address for LISTEN |
| SETLFS | $FFBA | 65466 | Set up a logical file |
| SETMSG | $FF90 | 65424 | Set system message output |
| SETNAM | $FFBD | 65469 | Set up file name |
| SETTIM | $FFDB | 65499 | Set the system clock |
| SETTMO | $FFA2 | 65442 | Set IEEE bus card timeout flag |
| STOP | $FFE1 | 65505 | Check if STOP key is pressed |
| TALK | $FFB4 | 65460 | Command a device on the serial bus to talk |
| TKSA | $FF96 | 65430 | Send a secondary address to a device commanded to talk |
| UDTIM | $FFEA | 65514 | Update the system clock |
| UNLSN | $FFAE | 65454 | Send an UNLISTEN command |
| UNTLK | $FFAB | 65451 | Send an UNTALK command |
| VECTOR | $FF8D | 65421 | Manage RAM vectors |
OPEN --------------------+
CHKIN/CHKOUT ---------+ |
begin a loop -----+ | |
input or output | | |
end a loop -------+ | |
CLRCHN ---------------+ |
CLOSE -------------------+
C64 U4 Kernal ROM Failure Symptoms[edit | edit source]
- Blank screen, no border.
- Most cartridges don't work but a few game carts (example: CBM Kickman and Jupiter Lander) will work with a normal screen because they bypass the Kernal ROM.
References[edit | edit source]
- ↑ Book Volkscomputer - Computer für die Masse 1981 - Startvorbereitungen, p. 114
- ↑ C64 Programmer's Reference Guide, p. 268: "The KERNAL"
- ↑ Video at YouTube 8-Bit Guy's channel: Commodore History Part 3 - The Commodore 64 (remark on the writing of "KERNAL" at 0:05:00)
Links[edit | edit source]
|
Wikipedia: Kernal |
