TurboForth V1.2.1:4 RAM Usage

Updated 11 May 2015

TurboForth uses the following memory:

CPU RAM

Vectors

Address	Value (hex)	Label/Name	Size (bytes)	Description
Note: the locations of these vectors MUST NOT change between releases
A000	0000	intvec	2	vector for INTERPRET >a000
A002	0000	blkvec	2	vector for BLOCK
A004	0000	numvec	2	vector for NUMBER
A006	0000	fndvec	2	vector for FIND
A008	0000	usrisr	2	vector for user isr
A00A	0000	kdel	2	Keyboard auto-repeat initial delay/2 (high-byte) and repeat delay (low byte)
A00C	0000	dsrvec	2	pointer to DSRLNK vector in bank 1
A00E	0000	gplvec	2	pointer to GPLLNK vector in bank 1
A010	0000	padvec	2	pointer to scratchpad restore code in bank 1
A012	8300	wp	2	Assembly language vector for returning to TF from external assembly code that runs in a different workspace. External assembly code (for example, code written with the TF assembler) that changes workspace can simply perform a BLWP @>A012 to restore TF's workspace and jump to NEXT in the inner interpreter, which will restore normal Forth execution perfectly. Software can actually change TF's workspace while running. A copy of the desired workspace address MUST be written here so that KEY can restore the correct workspace address after its call into the TI ROM.
A014	0000	pnext	2	pointer to NEXT's executable code
A016	0000	pdocon	2	pointer to DOCON's executable code
A018	0000	pcreate	2	pointer to CREATE's executable code

Memory Space Pointers

Address	Value (hex)	Label/Name	Size (bytes)	Description
A01A	0000	ffailm	2	first free address in low memory pointer
A01C	0000	ffaihm	2	first free address in hi memory pointer

Stack Pointers

Address	Value (hex)	Label/Name	Size (bytes)	Description
A01E	0000	s0	2	reserved for FORTH variable S0 - holds the address of the start of the data stack (r4)
A020	0000	rs0	2	address of start of return stack (r5)

Screen, keyboard and File I/O

Address	Value (hex)	Label/Name	Size (bytes)	Description
A022	0000	keydev	2	keyboard device to use for KSCAN routine in console ROM
A024	0000	cursrd	2	cursor delay used in KEY and the editor
A026	0000	noscrl	2	data to determine if screen scrolling should be suppressed. >0=suppress
A028	0000	scrX	2	x (column) co-ordinate of next character to be displayed on screen
A02A	0000	scrY	2	y (row) co-ordinate of next character to be displayed on screen
A02C	0000	xmax	2	screen width - 32, 40 or 80
A02E	0000	ymax	2	screen height - always 24
A030	0000	wrap	2	used to determine if wrap-around is used by SCROLL
A032	0000	panxy	2	starting screen address (top left) of panel
A034	0000	panr	2	number of rows in panel
A036	0000	panc	2	number of columns in panel
A038	0000	errnum	2	holds io error number of last error

Speech Synthesis

Address	Value (hex)	Label/Name	Size (bytes)	Description
A03A	0000	spcnt	2	number of bytes remaining in speech buffer
A03C	0000	spadr	2	address of next byte in speech buffer
A03E	0000	spcsvc	2	speech service: address of the speech service which should be called
A040	0000	synyes	2	0=speech synth not fitted. >FFFF=speech synth detected

Parsing & Compilation

Address	Value (hex)	Label/Name	Size (bytes)	Description
A042	0000	in	2	holds the current index into the terminal input buffer (TIB) - used by variable >IN
A044	0000	latest	2	reserved for FORTH variable LATEST, which points to the most recently defined word in the dictionary
A046	0000	here	2	points to the next free byte of memory. When compiling, compiled words go HERE
A048	0000	_state	2	is the interpreter interpreting (0) or compiling a word (!=0)
A04A	0000	tibsiz	2	characters per line: 80 on command line, 64 in blocks
A04C	0000	_span	2	the number of characters received by EXPECT. See variable #TIB
A04E	0000	doboot	2	"we're booting" flag (>0=booting)
A050	0000	sdelim	2	stores the end of string marker (normally ") for S". the word .( sets it temporarily to a ) character
A052	0000	isdbl	2	flag to indicate if NUMBER pushed a double (>0=yes)
A054	0000	dpl	2	decimal point location. set by NUMBER (doubles only)
A056	0000	cassen	2	if 0 dictionary searches are case sensitive
A058	0000	source	2	source-id. -1=string (via evaluate). 0=user input (keyboard/block)
A05A	0000	dotsin	2	flag for .S to use signed or unsigned numbers
A05C	0000	base	2	the current base for printing and reading numbers (would normally be 10 or 16)
A05E	0000	lbase	2	last number base, used by Number to String routine
A060	0000	expcnt	2	exponent count, used by Number to String routine
A062	0000	lzi	2	leading zero indicator, used by N>S routine to determine if leading 0's are ignored
A064	0000	dosign	2	flag for NTS routine. If >0, then NTS will treat numbers as unsigned, set by U. and .
A066	0000	_warn	2	redefinition warnings are suppressed if _warn=0
A068	0000	coding	2	!0 if CODE: compiling is active
A06A	0000	patch	2	holds the CFA of latest word created with CREATE in case DOES> needs to patch it

Miscellaneous

Address	Value (hex)	Label/Name	Size (bytes)	Description
A06C	0000	vdpr1	2	copy of vdp register 1 (stored at 83d4)
A06E	0000	retbnk	2	holds bank number to return to as a memory address (>6000 or >6002)
A070	0000	temp	2	for temporary storage
A072	0000	temp2	2	for temporary storage
A074	0000	temp3/seed	2	for temporary storage
A076	0000	seedc	2	seed for random number generation
A078	0000	sumode	2	graphics mode selected from cartridge menu screen

Editor Variables - used by the built in editor

Address	Value (hex)	Label/Name	Size (bytes)	Description
note: These variables use the same addresses as the compiler reference counters (below). This is safe to do, as the compiler is never in use when the editor is in use, and vice versa. Hence it makes sense to use the same addresses and save some valuable user RAM in low-memory. I'm nice like that.
A07A	0000	epage	2	holds block editor page
A07C	0000	csrx	2	cursor x for editor
A07E	0000	csry	2	cursor y for editor
A080	0000	csrflg	2	cursor blink flag for editor
A082	0000	autorp	2	keyboard auto repeat counter
A084	0000	autorl	2	keyboard auto repeat re-load value
A086	0000	edblk	2	block number of the block currently being edited

Compiler Security Reference Counters

Address	Value (hex)	Label/Name	Size (bytes)	Description
A07C	0000	ifcnt	2	incremented by IF, decremented by THEN
A07E	0000	docnt	2	incremented by DO, decremented by LOOP & +LOOP
A080	0000	forcnt	2	incremented by FOR, decremented by NEXT
A082	0000	cascnt	2	incremented by CASE, decremented by ENDCASE
A084	0000	ofcnt	2	incremented by OF, decremented by ENDOF
A086	0000	begcnt	2	incremented by BEGIN, decremented by UNTIL, REPEAT & AGAIN

Sprite Buffers

Address	Value (hex)	Label/Name	Size (bytes)	Description
A088	0000	sal	128	sprite attribute list
A108	0000	smlist	64	sprite movement list

File I/O Persistable Data

Address	Value (hex)	Label/Name	Size (bytes)	Description
A148	0000	sav8a	2	save data following blwp @dsrlnk (8 or >a)
A14A	0000	savcru	2	cru address of the peripheral
A14C	0000	savent	2	entry address of dsr or subprogram
A14E	0000	savlen	2	device or subprogram name length
A150	0000	savpab	2	pointer to device or subprogram in the pab
A152	0000	savver	2	version # of dsr
A154	0000	flgptr	2	pointer to flag in pab (byte 1 in pab)
A156	0000	dsrlws	10	dsrlnk workspace
A160	0000	dstype	22	dsrlnk workspace
A176	0000	haa	2	used to store AA pattern for DSR ROM detection
A178	0000	namsto	8	dsrlnk 8 bytes device name buffer

Scratch Peripheral Address Block (used for block I/O)

Address	Value (hex)	Label/Name	Size (bytes)	Description
A180	00	pabopc	1	opcode: open, read, etc
A181	00	pabflg	1	error code & file type
A182	0000	pabbuf	2	vdp address of data
A184	00	pablrl	1	logical record length
A185	00	pabcc	1	output character count
A186	0000	pabrec	2	record number
A188	00	pabsco	1	screen offset for char
A189	00	pabnln	1	name length
A18A	0000	pabfil	32	file name starts here

File Allocation Table

Address	Value (hex)	Label/Name	Size (bytes)	Description
A1AA	0000	falloc	6	Allocation table for file IO. At run time, these 3 cells are filled with addresses f1pab, f2pab & f3pab (see VDP RAM table). The MSB is set when a file is in use (i.e. when opened with #OPEN). The MSB is reset when #CLOSE is executed, and thus the file 'slot' can be re-used.

Block Related Data

Address	Value (hex)	Label/Name	Size (bytes)	Description
A1B0	0000	totblk	2	number of block buffers available
A1B2	0000	blknum	2	holds the block currently being compiled by INTERPRET
A1B4	0000	lstblk	2	holds the block currently being worked on
A1B6	0000	blk0	2	block number of the block stored in buf0 (0=unassigned)
A1B8	0000		2	VDP address of block0 MSB=1=dirty block
A1BA	0000	blk1	2	block number of the block stored in buf1 (0=unassigned)
A1BC	0000		2	VDP address of block1 MSB=1=dirty block
A1BE	0000	blk2	2	block number of the block stored in buf2 (0=unassigned)
A1C0	0000		2	VDP address of block2 MSB=1=dirty block
A1C2	0000	blk3	2	block number of the block stored in buf3 (0=unassigned)
A1C4	0000		2	VDP address of block3 MSB=1=dirty block
A1C6	0000	blk4	2	block number of the block stored in buf4 (0=unassigned)
A1C8	0000		2	VDP address of block4 MSB=1=dirty block
A1CA	0000	blk5	2	block number of the block stored in buf5 (0=unassigned)
A1CC	0000		2	VDP address of block5 MSB=1=dirty block
note: the vdp addresses of the block buffers are defined in 1-15-Initialise.a99

Stacks and Buffers

Address	Value (hex)	Label/Name	Size (bytes)	Description
A1CE	3420	tibadr	2	address of the terminal input buffer in VDP memory
A1D0	0000	wrdbuf	80	buffer for holding a word string. WORD copies a word string here from the terminal input buffer in VDP RAM.
A222	0000	wrkbuf	32	work buffer for Number to String routine (holds exponents)
A242	0000	strbuf	18	string buffer for Number to String routine to construct a string in

Data Stack and Return Stack

Address	Value (hex)	Label/Name	Size (bytes)	Description
A254	0000	retstk	52	return stack
A2C6	0000	dstack	62	data stack
note: both stacks grow towards lower memory addresses

User Program Space

User programs start immediately after the stacks, and grow (towards higher memory addresses) towards >FFFF. Note: The 8K section of the 32K RAM is also available for user programs, by changing the variable H to a memory address in low RAM. H tracks the current compilation address (HERE simply reads H). By changing it, you can change the address that the compiler will compile to. Dictionary linkage works normally. Take care when using MARKER when programs are split across high/low memory addresses, as invoking MARKER may leave the current compilation in the wrong memory bank!

Example of compiling to HIGH and LOW memory:

Note: TurboForth output is shown below in green.

FFAILM @ H ! \ set H to first free addes in low memory
: FOO CR ." FOO! " ;

FFAIHM @ H ! \ set H to first free address in high memory
: BAR ." BAR!" CR ;

FOO BAR

FOO! BAR!
ok:0

' FOO $.
2008 ok:0

' BAR $.
A2C8 ok:0