Loadstar 128 #25

home *** CD-ROM | disk | FTP | other *** search

/ Loadstar 128 #25 / q25.d81 / t.control80 2 < prev next >

Wrap

Text File | 1991-01-01 | 14.5 KB | 342 lines

*** Control 80 V1.21 *** by Jon Mattson One of the greatest advantages of upgrading from a C-64 to a C-128 has got to be the 80-column RGB capability. The improved resolution of the 8563 chip puts the 128 on par with its much more expensive rivals from a graphics point of view. Text displays, such as those used in word processors, benefit tremendously from the extra screen capacity, allowing the 128 to be used as a serious work machine. For the not-so-serious, adventure games and the like can also take advantage of this extra space. Then, too, there are all sorts of nifty graphic tricks that can be produced with the 8563. Unfortunately, 'tricks' might well be the operative word in that last paragraph. If you have tried programming the 8563 at all, you probably discovered early on that it was no task to be taken lightly. Using it at all can be quite a sleight of hand trick, in itself. Since the chip has only a two byte 'window' into the 128's normal memory, even apparently simple tasks can be daunting. Machine language knowledge is a virtual necessity for speedy graphics, since BASIC 7.0 virtually ignores the chip's existence. Even the tried and true POKE and PEEK don't work! Thus, if you aren't an ML wizard with a Programmer's Reference Guide, you probably had to content yourself with PRINT and the occasional SYS to ROM tricks. That was until now. CONTROL80 changes all of that by adding 18 new keywords to BASIC 7.0: 16 commands and 2 functions that give you full and easy access to the 8563. (See Foreword on the new MEGA command) Using C80 is simple. Just BLOAD it into memory and SYS 4864, either in direct mode or early on in your program. If you are in direct mode, a message will inform you that it is installed. This message will not appear from within a program, however, since it might ruin your screen presentation. Generally, a simple BLOAD will suffice, but, if you have been playing around with BANKs and the like, you might want to use the full syntax: BLOAD "CONTROL80",U(DV),B0,P4864 where DV is the current drive # Once C80 is installed, the new keywords can be used just like any other BASIC commands. You can even abbreviate them by shifting the second letter, as usual. Remember that C80 must be active (not just resident) while you type in a program using its keywords, or they will not be tokenized correctly. Note also that C80 uses memory from 4864 to 6629 (only), so avoid POKEing around this area. Hitting the beloved STOP/RESTORE combination will not deactivate C80. The QUIT command (previously unimplemented on the 128) will turn it off, although SYS 4864 will bring it back to life. Resetting the computer will also turn it off; however, due to its location, C80 will still be resident for later use as long as you haven't POKEd over its memory space. Now let's take a look at your new resources. Certain conventions have been followed in this listing. Memory addresses are 0-65535, as usual, to allow use with both 16K and 64K VDCs. Note, however, that addresses above 16383 wrap around on the 16K chip (i.e. 16384 = 0). Remember that the basic 8563 chip is set up as follows: $0000 - 07FF 0 - 2047 Screen $0800 - 0FFF 2048 - 4095 Attribute $1000 - 1FFF 4096 - 8191 Unused $2000 - 2FFF 8192 - 12287 Upper Case/Graphic Char Set $3000 - 3FFF 12288 - 16383 Lower/Upper Case Char Set VDC register numbers (reg# below) range from 0-36. While it is not within the scope of this article to explain the use of every register, a simplified table listing each one will be given in the Appendix. A more complete description can be found in the C-128 Programmer's Reference Guide and many other sources. When in doubt, experiment with WVD - just be sure that you check the registers normal value with RVD first to set things back to normal! *** FUNCTIONS PEER (VDC address) This function allows you to check the contents of VDC memory. It operates just like BASIC's PEEK. For example, to find the character in the top left corner of the screen: PRINT PEER(0). Note that PEER is the counterpart of POST, below. RVD (reg#) This function (Read ViDeo register) allows you to check the contents of any of the 37 VDC registers. For example, A=RVD(12) would put the contents of register 12 in A. Note that RVD is the counterpart of WVD, below. *** COMMANDS BLOCK VDC address, number, value This command is similar to FILL, below, except that it allows you to fill ANY small section of VDC memory with a single value. "Address" indicates the starting position of the fill, and "number" (2-255) indicates how many locations to fill with the specified "value" (0-255) from that point on. One of the best uses of BLOCK is to highlight a line on the screen by filling attribute memory with a different color value and/or reverse. For example, BLOCK 2048,80,72 would highlight the entire first line of the screen by coloring it red and using reverse characters. DUMP type This command dumps the entire 80 column screen display to any Commodore compatible printer. Remember that the 8563 allows two character sets on the screen at the same time, but your printer will not: it will print the entire screen with the character set specified. "Type" may be either 0 for an upper case/graphics dump or 7 for a lower/upper case dump. These correspond to the normal and alternate character sets, respectively, in VDC terms. If you must access DUMP in direct mode, remember that you can use ESCAPE-X to move to the 40-column screen and type the command there. If your printer is numbered 5 rather than 4, you can POKE the number into location 5965 and the screen will be dumped to Printer #5. For instance: POKE5965,5:DUMP7 FCOPY address, bank, character set This command allows you to convert and copy a standard 40-column font already in normal memory at the "address" and "bank" specified to the 8563 chip. Since the 8563 allows two character sets simultaneously, you must specify which one to replace: 0 for upper case/graphics or 1 for lower/upper case. For example, if you wanted to replace the uc/g set with your font, you might enter the following: BLOAD "font",U(DV),B0,P14336:FCOPY 14336,0,0 Note that you cannot simply VLOAD the font into 8563 memory, as the two formats are different and require conversion. Once the font has been FCOPYed into the VDC, you could VSAVE that, but it is actually less efficient this way, taking up twice as much disk space and thus, twice as much loading time. Stick with FCOPY if at all possible. FILL screen type, value This command allows you to fill either screen ("type" 0) or attribute ("type" 1) memory with a single "value" from 0-255. Screen codes are as per usual. Attribute codes include color, reverse, flash and the like: Bit 7 (128) Alternate Character Set 6 (64) Reverse Video 5 (32) Underline 4 (16) Flash 3 (8) Red 2 (4) Green 1 (2) Blue 0 (1) Intensity For example, FILL 1,154 will cause all characters to turn purple, flash and use the alternate character set. FINIT This command simply reinitializes the 8563's normal fonts. It is useful for cancelling the effects of FCOPY or undesirable POSTs into character memory. HOME Homes the cursor within the current window. LCLEAR first line, last line This command clears the indicated lines (0-24), including any unusual attribute effects such as flash and the like. Naturally, the last line must be higher than or equal to the value of the first. Note that lines are only cleared within the boundaries of the current window, and the line values will be offset by the position of the window from the real top of the screen. Thus, the 0-24 range assumes a full-screen window and will be smaller for smaller windows. POST VDC address, value This command allows you to place values into 8563 memory. It operates just like BASIC's POKE. For example, POST 0,1 will place an "A" in the top left corner of the screen. Note that POST is the counterpart of PEER. RECALL bytes, VDC address, from RAM address, from bank This command copies chunks of memory from normal RAM to 8563 VDC RAM. "Bytes" (1-65535) indicates the number of bytes to copy. "Address" and "bank" ranges are as per usual, 0-65535 and 0-15 respectively. When used in conjunction with STORE, this command can create "pop up" windows. For example, after opening up some free RAM space with GRAPHIC1,1:GRAPHIC5, you could use the following procedure: 1) STORE 4096,0,8192,0 to move the 4096 bytes of screen and attribute memory to location 8192 in bank 0. 2) Open the window as per usual. 3) When you are finished with the window, have the original screen reappear with RECALL 4096,0,8192,0. STORE bytes, VDC address, to RAM address, to bank This command copies chunks of memory from 8563 RAM to normal RAM. It is the reverse of, but otherwise similar to, RECALL, above. VCOL background, foreground This command alters the background and default foreground colors of the screen. Note that the foreground color is actually used very little, unless you turn off the screen attributes. As usual, color values must range from 1-16; however, since some of these values are not the same as on the 40- column screen, you may wish to experiment a bit. VLOAD "filename", VDC start address This command works in much the same manner as BLOAD except that data is loaded into VDC memory. The starting address is optional and defaults to the location from which the data was saved. Remember that variable strings used for filenames must be enclosed in parentheses. Note that BLOAD/BSAVE and VLOAD/VSAVE are compatible: memory VSAVEd from the VDC can be BLOADed to normal RAM and vice versa. Whether or not the data will have any meaning in this new context is another matter. VLOAD (and VSAVE below) both access drive 8 by default. Since you will want your program to work from any drive, you should make this POKE before using VLOAD or VSAVE: POKE6111,DV where DV is the current drive (found by PEEKing 186) VSAVE "filename", VDC start address, VDC end address+1 This command works in much the same manner as BSAVE except that data is saved from VDC memory. As with VLOAD, you should set the drive number by PEEKing 186 and POKEing this value into 6111 before calling VSAVE. WVD reg#, value This command (Write to ViDeo register) allows you to write directly to the 8563 registers. For example, WVD 26,242 would put 242 in register 26, altering the screen color. This command is the counterpart of the RVD function. Note that some registers have bits which cannot be directly altered by the user; thus, the value you enter with WVD may look different if you later RVD the same register. QUIT This command simply turns off C80. SYS 4864 to reactivate it. Do this and FINIT before exiting your program. MINE This is perhaps the most unusual command of all and is aimed mainly at machine language programmers. Normally, issuing MINE will give an UNIMPLEMENTED COMMAND error. (Note! See Foreword for details on the new included MINE function.) However, by POKEing an address into memory locations 6628-6629 (low byte/high byte format), you will cause the MINE command to execute a machine language routine of your creation at this location. If your routine is relatively short (less than 542 bytes), you can even POKE or BLOAD it directly into C80 by starting at address 6627, skipping the usual jump. The demo program uses this idea to have MINE create "rotating characters". Note that positioning your routine in this area allows you to BSAVE a new version of C80 containing your command. Another good place to put this routine is in the mostly unused area from $B00 to $BFF, since it is also in common RAM and will allow you to avoid banking hassles. "POKE 6628,0: POKE 6629,11" will set this up. You can even have more than one MINE routine in memory at the same time, altering the 6628-6629 jump vector as required to switch between them. (Note! MEGaBasic uses 4 pages of memory, from $0B00 to $0EFF for a 'staging' area, where its routines are installed and executed. This has two ramifications. First, if you want to use RAMDOS, use page $0F. Second, if your routines are written to reside here, MEGaBasic will clobber them if used. Make sure you install them at the start of your BASIC program each time it is run.) If you would like the MINE command to take in parameters, the following coding will usually do the trick: JSR $0380 JSR $AF96 JSR $AF0C For the first value, use JSR $0386 instead of $0380. Then place this routine in your code to retrieve each other parameter: it will return the low byte in the Y-Register and the high byte in the Accumulator. For example, MINE 1026 would return 2 in Y and 4 in A. Commas are automatically handled. If you want to save some space, this is already a built-in subroutine in C80 at $14C1 (decimal 5313), i.e. the three can be replaced with JSR $14C1. I have included a demo program to get you used to the capabilities of the new commands. It is, frankly, fairly simplistic, since most of the commands are designed to be useful rather than flashy. By LISTing it, however, you should get a better feel for the program's many talents and how to put them to use for you. *** Appendix REG FUNCTION 0 Horizontal total 1 Horizontal displayed 2 Horizontal sync position 3 Vert/Horiz sync width 4 Vertical total 5 Vertical total adjust 6 Vertical displayed 7 Vertical sync position 8 Interlace mode 9 Character total vertical 10 Cursor mode, start scan 11 Cursor end scan line 12 Display start address high 13 Display start address low 14 Cursor position high 15 Cursor position low 16 Light pen vertical 17 Light pen horizontal 18 Update address high 19 Update address low 20 Attribute start address high 21 Attribute start address low 22 Character horizontal displayed/total 23 Character displayed vertical 24 Vertical smooth scroll 25 Horizontal smooth scroll 26 Foreground/background color 27 Address increment/row 28 Character base address 29 Underline scan line count 30 Block copy word count 31 Data 32 Block copy source address high 33 Block copy source address low 34 Display enable begin 35 Display enable end 36 8563 DRAM refresh/scan line * Note: The 8563 registers use a high/low byte format instead of the usual low/high. JM \\\\\ RETURN - Menu \\\\\