c64mem_src.txt

- C64 RAM Map (Microsoft/Commodore)
-
- The labels and descriptions have been taken from
-    Microsoft's original BASIC for M6502 source
- and
-    The original C64 KERNAL source by Commodore (901227-03)
-  https://github.com/mist64/cbmsrc
-
- Converted and formatted by Michael Steil <mist64@mac.com>
-
- 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 13.
# * The description starts at column 21.
# * All lines of the description until the first blank line are
#   combined into the heading.
# * A '.' character at the end of a heading line represents a hard
#   line break.
# * The remaining text is in MarkDown format.
# * All addresses are 4 digits and have a leading '$'.
# The encoding is UTF-8.

#
# KERNAL
#

$0000        D6510   6510 data direction register
$0001        R6510   6510 data register

#
# BASIC
#

$0003-$0004  ADRAY1  Store here the addr of the
                     routine to turn the FAC into a
                     two byte signed integer in [Y,A]

$0005-$0006  ADRAY2  Store here the addr of the
                     routine to convert [Y,A] to a floating
                     point number in the FAC.

$0007        CHARAC  A delimiting character.

$0007        INTEGR  A one-byte integer from "QINT".

$0008        ENDCHR  The other delimiting character.

$0009        TRMPOS  Position of terminal carriage.

$000B        COUNT   A general counter.

$000C        DIMFLG

                     In getting a pointer to a variable
                     it is important to remember whether it
                     is being done for "dim" or not.

                     DIMFLG and VALTYP must be
                     consecutive locations.

$000D        VALTYP  The type indicator.

                     0=numeric 1=string.

$000E        INTFLG  Tells if integer.

$000F        GARBFL  Whether to do garbage collection.

$000F        DORES   Whether can or can't crunch res'd words.

                     Turned on when "data"
                     being scanned by crunch so unquoted
                     strings won't be crunched.

$0010        SUBFLG  Flag whether sub'd variable allowed.

                     "FOR" and user-defined function
                     pointer fetching turn
                     this on before calling "PTRGET"
                     so arrays won't be detected.
                     "STKINI" and "PTRGET" clear it.
                     Also disallows integers there.

$0011        INPFLG  Flags whether we are doing "INPUT"
                     or "READ".

$0012        TANSGN  Used in determining sign of tangent.

$0012        DOMASK  Mask in use by relation operations.

$0013        CHANNL  Holds channel number.

$0014-$0015  LINNUM  Location to store line number before BUF
                     so that "BLTUC" can store it all away at once.

                     A comma (preload or from ROM)
                     used by input statement since the
                     data pointer always starts on a
                     comma or terminator.

$0014-$0015  POKER   Set up location used by POKE.

                     Temporary for input and read code

$0016        TEMPPT  Pointer at first free temp descriptor.

                     Initialized to point to TEMPST.

$0017-$0018  LASTPT  Pointer to last-used string temporary.

$0019-$0021  TEMPST  Storage for NUMTMP temp descriptors.

$0022-$0025  INDEX   Indexes.

$0022-$0023  INDEX1

$0024-$0025  INDEX2

$0026        RESHO   Result of multiplier and divider.

$0027        RESMOH  One more byte.

$0028        RESMO

$0028        ADDEND  Temporary used by "UMULT".

$0029        RESLO

$002B-$002C  TXTTAB  Pointer to beginning of text.

                     Doesn't change after being
                     setup by "INIT".

$002D-$002E  VARTAB  Pointer to start of simple
                     variable space.

                     Updated whenever the size of the
                     program changes, set to [TXTTAB]
                     by "SCRATCH" ("NEW").

$002F-$0030  ARYTAB  Pointer to beginning of array
                     table.

                     Incremented by 6 whenever
                     a new simple variable is found, and
                     set to [VARTAB] by "CLEARC".

$0031-$0032  STREND  End of storage in use.

                     Increased whenever a new array
                     or simple variable is encountered.
                     set to [VARTAB] by "CLEARC".

$0033-$0034  FRETOP  Top of string free space.

$0035-$0036  FRESPC  Pointer to new string.

$0037-$0038  MEMSIZ  Highest location in memory.

$0039-$003A  CURLIN  Current line #.

                     Set to 0,255 for direct statements.

$003B-$003C  OLDLIN  Old line number

                     Set up by ^C,"STOP"
                     or "END" in a program.

$003D-$003E  OLDTXT  Old text pointer.

                     Points at statement to be exec'd next.

$003F-$0040  DATLIN  Data line # -- remember for errors.

$0041-$0042  DATPTR  Pointer to data.

                     Initialized to point
                     at the zero in front of [TXTTAB]
                     by "RESTORE" which is called by "CLEARC".
                     updated by execution of a "READ".

$0043-$0044  INPPTR  This remembers where input is coming from.

$0045-$0046  VARNAM  Variable's name is stored here.

$0047-$0048  VARPNT  Pointer to variable in memory.

$0047        FDECPT  Pointer into power of tens of "FOUT".

$0049-$004A  FORPNT  A variable's pointer for "FOR" loops
                     and "LET" statements.

$0049        LSTPNT  Pntr to list string.

$0049        ANDMSK  The mask used by WAIT for ANDing.

$004A        EORMSK  The mask for EORing in wait.

$004B-$004C  OPPTR   Pointer to current op's entry in "OPTAB".

$004B        VARTXT  Pointer into list of variables.

$004D        OPMASK  Mask created by current operator.

$004E-$0052  TEMPF3  A third FAC temporary (4 bytes).

$004E-$004F  DEFPNT  Pointer used in function definition.

$004E        GRBPNT  Another used in garbage collection.

$0050-$0052  DSCPNT  Pointer to a string descriptor.

$0053        FOUR6   Variable constant used by garb collect.

$0054-$0056  JMPER

$0055        SIZE

$0056        OLDOV   The old overflow.

$0057-$005B  TEMPF1

$0058        HIGHDS  Destination of highest element in BLT.

$005A        HIGHTR  Source of highest element to move.

$005C-$0060  TEMPF2

$005D        LOWDS   Location of last byte transferred into.

$005F        LOWTR   Last thing to move in BLT.

$0058        ARYPNT  A pointer used in array building.

$005F        GRBTOP  A pointer used in garbage collection.

$005D        DECCNT  Number of places before decimal point.

$005E        TENEXP  Has a DPT been input?

$005F        DPTFLG  Base ten exponent.

$0060        EXPSGN  Sign of base ten exponent.

$0061-$0066  FAC     The floating accumulator

$0061        FACEXP

$0061        DSCTMP  This is where temp descs are built.

$0062        FACHO   Most significant byte of mantissa.

$0063        FACMOH  One more.

$0064        FACMO   Middle order of mantissa.

$0064        INDICE  Indice is set up here by "QINT".

$0065        FACLO   Least sig byte of mantissa.

$0066        FACSGN  Sign of FAC (0 or -1) when unpacked.

$0067        SGNFLG  Sign of FAC is preserved bere by "FIN".

$0067        DEGREE  A count used by polynomials.

$0068        BITS    Something for "SHIFTR" to use.

$0069-$006E          The floating argument (unpacked)

$0069        ARGEXP

$006A        ARGHO

$006B        ARGMOH

$006C        ARGMO

$006D        ARGLO

$006E        ARGSGN

$006F        ARISGN  A sign reflecting the result.

$006F-$0070  STRNG1  Pointer to a string or descriptor.

$0070        FACOV   Overflow byte of the FAC.

$0071-$0072  FBUFPT  Pointer into FBUFFR used by FOUT.

$0071-$0072  BUFPTR  Pointer to buf used by "CRUNCH".

$0071-$0072  STRNG2  Pointer to string or desc.

$0071-$0072  POLYPT  Pointer into polynomial coefficients.

$0071-$0072  CURTOL  Absolute linear index is formed here.

$0073-$008A  CHRGET  RAM code.

                     This code gets changed throughout execution.
                     It is made to be fast this way.
                     Also, [X] and [Y] are not disturbed.
                     
                     "CHRGET" using [TXTPTR] as the current text pntr,
                     fetches a new character into ACCA after incrementing [TXTPTR]
                     and sets condition codes according to what's in ACCA.

                     * not C = numeric ("0" thru "9")
                     * Z = ":" or end-of-line (a null)

                     [ACCA] = new char.
                     
                     [TXTPTR]=[TXTPTR]+1

                     The following exists in ROM if ROM exists and is loaded
                     down here by init. Otherwise it is just loaded into this
                     RAM like all the rest of RAM is loaded.

$008B-$008F  RNDX    

#
# KERNAL
#

$0090        STATUS  I/O operation status byte

$0091        STKEY   STOP key flag

$0092        SVXT    Cassette: temp used to adjust software servo

$0093        VERCK   Cassette: verify or load flag (Z - loading)

$0094        C3P0    IEEE buffered char flag

$0095        BSOUR   Char buffer for IEEE

$0096        SYNO    Cassette: flags if we have block SYNC (16 zero dipoles)

$0097        XSAV    Temp for BASIN

$0098        LDTND   Index to logical file

$0099        DFLTN   Default input device #

$009A        DFLTO   Default output device #

$009B        PRTY    Cassette: holds current calculated parity bit

$009C        DPSW    Cassette: if NZ then expecting LL/L combination that ends a byte

$009D        MSGFLG  OS message flag

$009E        PTR1    Cassette: count of read locations in error (pointer into bad, max 61)

$009E        T1      Temporary 1

$009F        PTR2    Cassette: count of re-read locations (pointer into bad, during re-read)

$009F        T2      Temporary 2

$00A0-$00A2  TIME    24 hour clock in 1/60th seconds

$00A3        R2D2    Serial bus usage

$00A3        PCNTR   Cassette: counts down from 8-0 for data then to ff for parity

$00A4        BSOUR1  Temp used by serial routine

$00A4        FIRT    Cassette: used to indicate which half of dipole we're in

$00A5        COUNT   Temp used by serial routine

$00A5        CNTDN   Cassette sync countdown

$00A6        BUFPT   Cassette buffer pointer

$00A7        INBIT   RS-232 rcvr input bit storage

$00A7        SHCNL   Cassette: holds FSBLK, used to direct routines, because of exit case

$00A8        BITCI   RS-232 rcvr bit count in

$00A8        RER     Cassette: flags errors (if Z then no error)

$00A9        RINONE  RS-232 rcvr flag for start bit check

$00A9        REZ     Cassette: counts zeros (if Z then correct # of dipoles)

$00AA        RIDATA  RS-232 rcvr byte buffer

$00AA        RDFLG   Cassette: holds function mode

                     MI - waiting for block SYNC
                     VS - in data block reading data
                     NE - waiting for byte SYNC

$00AB        RIPRTY  RS-232 rcvr parity storage

$00AB        SHCNH   Cassette: short cnt; left over from debugging

$00AC        SAL     Cassette: indirect to data storage area

$00AD        SAH

$00AE        EAL

$00AF        EAH

$00B0        CMP0    Cassette: software servo (+/- adjust to time calcs)

$00B1        TEMP    Cassette: used to hold dipole time during type calculations

$00B2-$00B3  TAPE1   Address of tape buffer #1y.

$00B4        BITTS   RS-232 trns bit count

$00B4        SNSW1   Cassette: flags if we have byte SYNC (a longlong)

$00B5        NXTBIT  RS-232 trns next bit to be sent

$00B5        DIFF    Cassette: used to preserve SYNO (outside of bit routines)

$00B6        RODATA  RS-232 trns byte buffer

$00B6        PRP     Cassette: has combined error values from bit routines

$00B7        FNLEN   Length current file n str

$00B8        LA      Current file logical addr

$00B9        SA      Current file 2nd addr

$00BA        FA      Current file primary addr

$00BB-$00BC  FNADR   Addr current file name str

$00BD        ROPRTY  RS-232 trns parity buffer

$00BD        OCHAR

$00BE        FSBLK   Cassette: indicate which block we're looking at (0 to exit)

$00BF        MYCH    Cassette: holds input byte being built

$00C0        CAS1    Cassette manual/controlled switch

$00C1        TMP0

$00C1        STAL

$00C2        STAH

$00C3-$00C4  MEMUSS  Cassette load temps (2 bytes)

$00C3-$00C4  TMP2

$00C5        LSTX    Key scan index

$00C6        NDX     Index to keyboard q

$00C7        RVS     RVS field on flag

$00C8        INDX

$00C9        LSXP    X pos at start

$00CA        LSTP

$00CB        SFDX    SHIFT mode on print

$00CC        BLNSW   Cursor blink enab

$00CD        BLNCT   Count to toggle cur

$00CE        GDBLN   Char before cursor

$00CF        BLNON   On/off blink flag

$00D0        CRSW    INPUT vs GET flag

$00D1-$00D2  PNT     Pointer to row

$00D3        PNTR    Pointer to column

$00D4        QTSW    Quote switch

$00D5        LNMX    40/80 max positon

$00D6        TBLX

$00D7        DATA    Cassette: holds most recent dipole bit value

$00D8        INSRT   Insert mode flag

$00D9-$00F2  LDTB1   Line flags+endspace

$00F3-$00F4  USER    Screen editor color IP

$00F5-$00F6  KEYTAB  Keyscan table indirect

$00F7-$00F8  RIBUF   RS-232 input buffer pointer

$00F9-$00FA  ROBUF   RS-232 output buffer pointer

$00FB-$00FE  FREKZP  Free KERNAL zero page 9/24/80

$00FF-$010A  BASZPT  Location ($00FF) used by BASIC

$0100-$013E  BAD     Cassette: storage space for bad read locations (bottom of stack)

#
# BASIC
#

$0200-$0258  BUF     BASIC/MONITOR buffer

                     Type-in stored here.
                     Direct statements execute out of
                     here. Remember "INPUT" smashes buf.
                     Must be on page zero
                     or assignment of string
                     values in direct statements won't copy
                     into string space -- which it must.
                     N.B.: Two nonzero bytes must precede "BUFLNM".

#
# KERNAL
#

$0259-$0262  LAT     Logical file numbers

$0263-$026C  FAT     Primary device numbers

$026D-$0276  SAT     Secondary addresses

$0277-$0280  KEYD    IRQ keyboard buffer

$0281-$0282  MEMSTR  Start of memory

$0283-$0284  MEMSIZ  Top of memory

$0285        TIMOUT  IEEE timeout flag

$0286        COLOR   Active color nybble

$0287        GDCOL   Original color before cursor

$0288        HIBASE  Base location of screen (top)

$0289        XMAX

$028A        RPTFLG  Key repeat flag

$028B        KOUNT

$028C        DELAY

$028D        SHFLAG  SHIFT flag byte

$028E        LSTSHF  Last SHIFT pattern

$028F-$0290  KEYLOG  Indirect for keyboard table setup

$0291        MODE    0-PET mode, 1-cattacanna

$0292        AUTODN  Auto scroll down flag(=0 on,<>0 off)

$0293        M51CTR  6551 control register

$0294        M51CDR  6551 command register

$0295-$0296  M51AJB  Non standard (bittime/2-100)

$0297        RSSTAT  RS-232 status register

$0298        BITNUM  Number of bits to send (fast response)

$0299-$029A  BAUDOF  Baud rate full bit time (created by open)

$029B        RIDBE   Input buffer index to end

$029C        RIDBS   Input buffer pointer to start

$029D        RODBS   Output buffer index to start

$029E        RODBE   Output buffer index to end

$029F-$02A0  IRQTMP  Holds irq during tape ops

$02A1        ENABL   RS-232 enables (replaces ier)

$02A2        CASTON  TOD sense during cassettes

$02A3        KIKA26  Cassette: holds old D1ICR after clear on read

$02A4        STUPID  Cassette: hold indicator (NZ - no T1IRQ yet) for T1IRQ

$02A5        LINTMP  Temporary for line index

$02A6        PALNTS  PAL vs NTSC flag 0=NTSC 1=PAL

#
# BASIC
#

$0300-$0301  IERROR  indirect ERROR (output error in .X)
$0302-$0303  IMAIN   indirect MAIN (system direct loop)
$0304-$0305  ICRNCH  indirect CRUNCH (tokenization routine)
$0306-$0307  IQPLOP  indirect LIST (char list)
$0308-$0309  IGONE   indirect GONE (char dispatch)
$030A-$030B  IEVAL   indirect EVAL (symbol evaluation)
$030C        SAREG   .A reg
$030D        SXREG   .X reg
$030E        SYREG   .Y reg
$030F        SPREG   .P reg
$0310-$0312  USRPOK  user function dispatch

#
# KERNAL
#

$0314-$0315  CINV    IRQ RAM vector

$0316-$0317  CBINV   BRK instr RAM vector

$0318-$0319  NMINV   NMI RAM vector

$031A-$032D          Indirects for code

                     Conforms to KERNAL spec 8/19/80

$031A-$031B  IOPEN   

$031C-$031D  ICLOSE  

$031E-$031F  ICHKIN

$0320-$0321  ICKOUT

$0322-$0323  ICLRCH

$0324-$0325  IBASIN

$0326-$0327  IBSOUT

$0328-$0329  ISTOP

$032A-$032B  IGETIN

$032C-$032D  ICLALL

$032E-$032F  USRCMD

$0330-$0331  ILOAD

$0332-$0333  ISAVE   savesp

$033C-$03FB  TBUFFR  cassette data b