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kernal_pm.txt
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kernal_pm.txt
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- C64 KERNAL API (Cracking the Kernal)
-
- Peter Marcotty: Cracking The Kernal
- COMPUTE! #40, September 1983, pp. 268-274
-
- Descriptions of RESTOR, SAVE and SCNKEY are missing from
- the original source!
-
- Corrections (typos as well as content), translations etc.
- welcome at: https://github.com/mist64/c64ref
-
----------------------------------------------
-
# This plain text file is formatted so that it can be automatically
# parsed in order to create cross-references etc.
# * Lines starting with "-" is top-level information. The first line
# is the title. Lines starting with "--" are separators.
# * Lines starting with "#" are internal comments.
# * Hex addresses start at column 0.
# * Symbols start at column 7.
# * The description starts at column 15.
# * All lines of the description until the first blank line are
# combined into the heading.
# * The remaining text is in MarkDown format.
# The encoding is UTF-8.
$FFA5 ACPTR Input byte from serial port.
ACPTR is used to get data off the serial bus. TALK and TKSA must be called first.
;Get a byte from the serial bus.
JSR ACPTR
STA $0800
;This example only shows the end result; call TALK and TKSA first.
$FFC6 CHKIN Open channel for input.
CHKIN is used to define any OPENed file as an input file. OPEN must be called first.
;Define logical file #2 as an input channel.
LDX #2
JSR CHKIN
;The X register designates which file #.
$FFC9 CHKOUT Open channel for output.
CHKOUT. Just like CHKIN, but it defines the file for output. OPEN must be called first.
;Define logical file #4 as an output file.
LDX #4
JSR CHKOUT
;Once again the X register defines the file #.
$FFCF CHRIN Input character from channel.
CHRIN will get a character from the current input device. Calling OPEN and CHKIN can change the input device.
;Store a typed string to the screen.
LDY #$00
LOOP JSR CHKIN
STA $0800,Y
INY
CMP #$0D
BNE LOOP
RTS
;This example is like an INPUT statement. Try running it.
$FFD2 CHROUT Output character to channel.
CHROUT. Load the accumulator with your number and call. OPEN and CHKOUT will change the output device.
;Duplicate the command of CMD 4:PRINT "A";
LDX #4
JSR CHKOUT
LDA #'A
JSR CHROUT
RTS
;The letter A is printed to the screen; call OPEN first for the printer.
$FFA8 CIOUT Output byte to serial port.
CIOUT will send data to the serial bus. LISTEN and SECOND must be called first. Call UNLSN to finish up neatly.
;Send the letter X to the serial bus.
LDA #'X
JSR CIOUT
RTS
;The accumulator is used to transfer the data.
$FF81 CINT Initialize screen editor.
CINT resets the 6567 video controller chip and the screen editor.
;Reset the 6567 chip and the 6566 VIC chip.
JSR CINT
RTS
;Basically, just like pressing the STOP and RESTORE keys.
$FFE7 CLALL Close all channels and files.
CLALL really does what its name implies-it closes all files and resets all channels.
;Close all files.
JSR CLALL
RTS
;The CLRCHN routine is called automatically.
$FFC3 CLOSE Close a specified logical file.
CLOSE. This routine will CLOSE any logical file that has been OPENed.
;Close logical file #2.
LDA #2
JSR CLOSE
;The accumulator designates the file #.
$FFCC CLRCHN Close input and output channels.
CLRCHN resets all channels and I/O registers - the input to keyboard and the output to screen.
;Restore default values to I/O devices.
JSR CLRCHN
RTS
;The accumulator and the X register are altered.
$FFE4 GETIN Get character from keyboard buffer.
GETIN will get one piece of data from the input device. OPEN and CHKIN can be used to change the input device.
;Wait for a key to be pressed.
WAIT JSR GETIN
CMP #0
BEQ WAIT
;If the serial bus is used, then all registers are altered.
$FFF3 IOBASE Return base address of I/O devices.
IOBASE returns the low and high bytes of the starting address of the I/O devices in the X and Y registers.
;Set the Data Direction Register of the user port to 0 (input).
JSR IOBASE
STX POINT
STY POINT+1
LDY #2
LDA #0
STA (POINT),Y
;POINT is a zero-page address used to access the DDR indirectly.
$FF84 IOINIT Initialize input/output.
IOINIT initializes all I/O devices and routines. It is part of the system's powering-up routine.
;Initialize all I/O devices.
JSR IOINIT
RTS
;All registers are altered.
$FFB1 LISTEN Command devices on serial bus to LISTEN.
LISTEN will command any device on the serial bus to receive data.
;Command device #8 to listen.
LDA #8
JSR LISTEN
;The accumulator designates the device #.
$FFD5 LOAD Load RAM from a device.
LOAD. The computer will perform either the LOAD or the VERIFY command. If the ac cumulator is a 1, then LOAD; if 0, then verify.
;Load a program into memory.
LDA #$08
LDX #$02
LDY #$00
JSR SETLFS
LDA #$04
LDX #L,NAME
LDY #H,NAME
JSR SETNAM
LDA #$00
LDY #$20
JSR LOAD
RTS
NAME .BY 'FILE'
;Program 'FILE' will be loaded into memory starting at 8192 decimal, X being the low byte and Y being the high byte for the load.
$FF9C MEMBOT Read/set bottom of memory.
MEMBOT. If the carry bit is set, then the low byte and the high byte of RAM are returned in the X and Y registers. If the carry bit is clear, the bottom of RAM is set to the X and Y registers.
;Move bottom of memory up one page.
SEC
JSR MEMBOT
INY
CLC
JSR MEMBOT
RTS
;The accumulator is left alone.
$FF99 MEMTOP Read/set top of memory.
MEMTOP. Same principle as MEMBOT, except the top of RAM is affected.
;Protect 1K of memory from BASIC.
SEC
JSR MEMTOP
DEY
CLC
JSR MEMTOP
;The accumulator is left alone.
$FFC0 OPEN Open a logical file.
OPEN. After SETLFS and SETNAM have been called, you can OPEN a logical file.
;Duplicate the command OPEN 15,8,15,'I/O'
LDA #3
LDX #L,NAME
LDY #H,NAME
JSR SETNAM
LDA #15
LDX #8
LDY #15
JSR SETLFS
JSR OPEN
RTS
NAME .BY 'I/O'
;OPEN opens the current name file with the current LFS.
$FFF0 PLOT Read/set X,Y cursor position.
PLOT. If the carry bit of the accumulator is set, then the cursor X,Y is returned in the Y and X registers. If the carry bit is clear, then the cursor is moved to X,Y as determined by the Y and X registers.
;Move cursor to row 12, column 20 (12,20).
LDX #12
LDY #20
CLC
JSR PLOT
;The cursor is now in the middle of the screen.
$FF87 RAMTAS Initialize RAM, reset tape buffer.
RAMTAS is used to test RAM, reset the top and bottom of memory pointers, clear $0000 to $0101 and $0200 to $03FF, and set the screen memory to $0400.
;Do RAM test.
JSR RAMTAS
RTS
;All registers are altered.
$FFDE RDTIM Read realtime clock.
RDTIM. Locations 160-162 are transferred, in order, to the Y and X registers and the accumulator.
;Store system clock to screen.
JSR RDTIM
STA 1026
STX 1025
STY 1024
;The system clock can be translated as hours/minutes/ seconds.
$FFB7 READST Read I/O status word.
READST. When called, READST returns the status of the I/O devices. Any error code can be translated as operator error.
;Check for read error.
JSR READST
CMP #16
BEQ ERROR
;In this case, if the accumulator is 16, a read error occurred.
$FF8A RESTOR Restore I/O default vectors.
$FFD8 SAVE Save RAM to device.
$FF9F SCNKEY Scan keyboard.
$FFED SCREEN Return X,Y organization of screen.
SCREEN returns the number of columns and rows the screen has in the X and Y registers.
;Determine the screen size.
JSR SCREEN
STX MAXCOL
STY MAXROW
RTS
;SCREEN allows further compatibility between the 64, the VIC-20, and future versions of the 64.
$FF93 SECOND Send secondary address after LISTEN.
SECOND. After LISTEN has been called, a SECONDary address may be sent.
;Address device #8 with secondary address #15.
LDA #8
JSR LISTEN
LDA #15
JSR SECOND
;The accumulator designates the address number.
$FFBA SETLFS Set logical, first, and second address.
SETLFS stands for SET Logical address, File address, and Secondary address. After SETLFS is called, OPEN may be called.
;Set logical file #1, device #8, secondary address of 15.
LDA #1
LDX #8
LDY #15
JSR SETLFS
;If OPEN is called, the command will be OPEN 1,8,15.
$FF90 SETMSG Control Kernal messages.
SETMSG. Depending on the accumulator, either error messages, control messages, or neither is printed.
;Turn on control messages.
LDA #$40
JSR SETMSG
RTS
;A 128 is for error messages; a zero, for turning both off.
$FFBD SETNAM Set filename.
SETNAM. In order to access the OPEN, LOAD, or SAVE routines, SETNAM must be called first.
;SETNAM will prepare the disk drive for'FILE#1'.
LDA #6
LDX #L,NAME
LDY #H,NAME
JSR SETNAM
NAME .BY 'FILE#1'
;Accumulator is file length, X is low byte, and Y is high byte.
$FFDB SETTIM Set realtime clock.
SETTIM is the opposite of RDTIM: it SETs the system clock instead of ReaDing it.
;Set system clock to 10 minutes =3600 jiffies.
LDA #0
LDX #L,3600
LDY #H,3600
JSR SETTIM
;This allows very accurate timing for many things.
$FFA2 SETTMO Set time-out on serial bus.
SETTMO is used only with an IEEE add-on card to access the serial bus.
;Disable time-outs on serial bus.
LDA #0
JSR SETTMO
;To enable time-outs, set the accumulator to a 128 and call SETTMO.
$FFE1 STOP Check for STOP key.
STOP will set the Z flag of the accumulator if the STOP key was pressed.
;Check for STOP key being pressed.
WAIT JSR STOP
BNE WAIT
RTS
;STOP must be called if the STOP key is to remain functional.
$FFB4 TALK Command serial bus device to TALK.
TALK. This routine will command a device on the serial bus to send data.
;Command device #8 to TALK.
LDA #8
JSR TALK
RTS
;The accumulator designates the file number.
$FF96 TKSA Send secondary address after TALK.
TKSA is used to send a secondary address for a TALK device. TALK must be called first.
;Signal device #4 to talk with command #7.
LDA #4
JSR TALK
LDA #7
JSR TKSA
RTS
;This example will tell the printer to print in uppercase.
$FFEA UDTIM Increment realtime clock.
UDTIM. If you are using your own interrupt system, you can update the system clock by calling UDTIM.
;Update the system clock.
JSR UDTIM
RTS
;It is useful to call UDTIM before calling STOP.
$FFAE UNLSN Command serial bus to UNLISTEN.
UNLSN commands all devices on the serial bus to stop receiving data.
;Command the serial bus to UNLiSteN.
JSR UNLSN
RTS
;The serial bus can now be used for other things.
$FFAB UNTLK Command serial bus to UNTALK.
UNTLK. All devices previously set to TALK will stop sending data.
;Command serial bus to stop sending data.
JSR UNTLK
RTS
;Sending UNTLK commands all talking devices to get off the serial bus.
$FF8D VECTOR Read/set vectored I/O.
VECTOR. If the carry bit of the accumulator is set, the start of a list of the current contents of the RAM vectors is returned in the X and Y registers. If the carry bit is clear, there the user list pointed to by the X and Y registers is transferred to the system RAM vectors.
;Change the input routines to new system.
SEC
JSR VECTOR
LDA #L,MYINP
STA USER+10
LDA #H,MYINP
STA USER+11
LDX #L,USER
LDY #H,USER
CLC
JSR VECTOR
RTS
USER .DE 26
;The new input list can start anywhere. USER is the location for temporary strings, and 35-36 is the utility pointer area.