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Custom_BASIC_Commands.md

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Custom BASIC Commands

Communicate with and through your TeensyROM from C64 BASIC

Implementation built upon Custom Basic Commands Copyright 2023 by Barry Walker
Thank you Barry for this well documented, robust framework!

To begin, select BASIC w/ Custom Commands +TR BAS from the main TR menu. (FW 0.6.2 or higher)

TeensyROM specific commands available:

Command Description
TSAVE <media><path><filename> Super fast Saves the current BASIC file to SD or USB on the TR
TLOAD <media><path><filename> Super fast Loads a BASIC file from SD or USB on the TR
TDIR <media><path> Display directory contents of TR media
TPUT <string out> Send the full contents of <string out> out the TR USB Serial port
TGET <string char in> Read a singe character from the TR USB Serial port into <string char in>
(for in-program use only)

Command argument details:

Argument Description Requirement
<media> Either USB: or SD: to specify media type optional, USB is default
<path> Path to file from root optional, root is default
<filename> Name of the program file required, use .prg extension

What can be done with these commands?

  • Instantly load and Save BASIC programs to/from your TR 
    TLOAD "MYPROG.PRG"
TSAVE "SD:MYDIR/TERM.PRG
TDIR
  • Communicate via USB serial to/from another computer.
    • See this brief demo video
    • Write BASIC programs that can receive/display externally provided data 
      10 B$ = ""
20 TGET A$ : B$ = B$ + A$
30 IF A$<>CHR$(13) THEN 20
40 PRINT "LINE RECEIVED: ";B$
50 GOTO 10
    • Send information or user input to another computer. 
      10 IF T$=TIME$ THEN 10 : REM LOOP UNTIL NEXT SECOND
20 T$=TIME$
30 TPUT LEFT$(T$,2)+":"+MID$(T$,3,2)+":"+RIGHT$(T$,2)
40 TPUT CHR$(10)+CHR$(13)
50 GOTO 10
    • Example simple terminal program: 
      10 GET A$ : TPUT A$
20 TGET B$ : PRINT B$;
30 GOTO 10

Capabilities included from the original implementation:

BASIC will now accept integers as either HEX or binary, in addition to decimal.
For example: POKE $0400, $0a or POKE $d020, %00001111.
You're not limited to 16-bit values, so PRINT $d00000 is perfectly valid.

Additional Commands

Note that some of these require additional HW such as an REU, or can conflict with memory space used by these commands themselves.

Command Description
BACKGROUND Sets the background color: Example: BACKGROUND 2 would set it to red
BORDER Sets the border color. Works the same as BACKGROUND
CLS Clears the screen. Nice and simple.
WOKE A 16-bit version of the POKE command. Example: WOKE $61, $0400 would put $00 into $61 and $04 into $62.
MEMCOPY A fast way to move bytes around in memory. Example: MEMCOPY $0428, $0400, $28 would copy the 2nd line of text to the first. This could be used to quickly scroll portions of the screen.
MEMFILL No more slow FOR/NEXT loops to POKE values into memory. Example: MEMFILL $0400, 1000, 32 would clear the default screen.
BANK Select the current VIC bank. Must be between 0-3 where 0 starts at $0000 and 3 starts at $c000. This affects all graphics on the machine including screen, chars and sprites
SCREEN Select the 1k offset for the current video screen. The default is 1 ($0400) in bank 0. Each bank can hold 16 screens (not all can be used for screen RAM), so the value here has to be between 0 and 15.
STASH Copy bytes from the C64 to an attached REU. Example STASH $0400, $0, 1000, 0 would copy the default screen to REU address $0 in bank $0.
FETCH Copy bytes from an attached REU to the C64. Example FETCH $0400, $0, 1000, 0 would copy bytes from REU address $0, bank $0 to the C64's default screen $0400
MEMLOAD Loads binary data from disk into memory. Example MEMLOAD "SHAPES.SPR",8,$8000 would load shape data from the file SHAPES.SPR to $8000, which is the start of VIC bank 2
MEMSAVE Saves binary data from memory to disk. Example MEMSAVE "@:SHAPES.SPR,P,W",$8000,$8040 would save the 64 bytes between $8000 and $8040 to a file named SHAPES.SPR
SPRSET Turn sprites on/off as well as set their pointer to their shape data.
SPRPOS Set a sprite's X and Y positions. X can be 0-511 and Y can be 0-255
SPRCOLOR Set a sprite's color
DIR Display a disk directory listing. Example DIR 8 would display the disk directory of a disk in device 8.

Additional functions

Function Description
WEEK A version of the PEEK function which returns a 16-bit word instead of an 8-bit byte. Example: PRINT WEEK($61)
SCRLOC Returns the absolute address for the start of screen RAM. At startup PRINT SCRLOC(0) would return 1024. You can use the BANK and SCREEN commands to relocate the screen.
REU Detect the type of attached REU, if any. Currently this is broken and needs some TLC.

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