erikmb@etek.chalmers.se (Erik Bryntse) (05/24/91)
Ok, here are a new version of S-CHIP. It is a lot faster than version
1.0 and have some new scroll functions. And it's still small!
I have copied parts of the original CHIP-48 documentation and added the
new functions that are available in S-CHIP.
If you would like to start writing games for CHIP, read this, get yourself
an assembler, look at someone else's program and get started! It's not
difficult, you can get something up and working in just an hour or so.
And you get the benefits of machine code - the speed - without having
to learn all the internals of the 48. And it won't crash when you do
something wrong (I hope...).
... and by the way, H. Piper is exactly the kind of super fantastic
games that I would like to see more of. Good work!
SUPER-CHIP v1.1
===============
... a modified version of the CHIP-8 game interpreter originally
made by Andreas Gustafsson.
S-CHIP offers:
- full screen resolution in new extended screen mode
- downward compability (you can run your old CHIP games)
- higher speed in extended mode
- a larger 16x16 sprite available
- new, larger fonts for scores
- you can pass information to and from a S-CHIP program
- programmable exit from the S-CHIP interpreter possible
- no need to turn off the clock
- it will always start
- instructions to scroll the screen down, left, and right
Introduction to CHIP
--------------------
For those who don't remember, the CHIP-8 programming language was
used in a number of home computers based on RCA's CDP1802 pro-
cessor in the late 1970's. It's a small, interpreted language
designed specifically for writing simple video games. It has
less than 40 instructions, including arithmetic, control flow,
graphics, and sound. The instructions are all 16 bits long and
are executed by a very compact virtual machine interpreter (the
1802 implementation was 512 bytes long).
Technical specification
-----------------------
The CHIP-8 virtual machine is byte-addressable and has an address
space of 4 kB at addresses 000-FFF hex. However, addresses
000-1FF are reserved (this is where the CHIP-8 interpreter used to
reside). Therefore, the CHIP-8 program itself begins at address
200. All instructions are 16 bits long and by convention instruc-
tions always start at an even address.
The machine has 16 8-bit general-purpose registers called V0..VF.
The VF register is modified by certain instructions and works as a
carry flag and sprite collision indicator. There is also a 16-bit
pointer register I (though only the low 12 bits are generally
used).
A CHIP-8 program displays graphics by drawing sprites that are 8
pixels wide and 1..15 pixels high. The screen resolution is 32 by
64 pixels in standard mode. The origin is the upper left corner
of the screen, and all coordinates are positive. The sprites are
stored in bigendian format, i.e., the most significant bit corre-
sponds to the leftmost pixel. All drawing is done in XOR mode. If
this causes one or more pixels to be erased, VF is <> 00, other-
wise 00.
In extended screen mode the resolution is 64 by 128 pixels. A
sprite of 16x16 size is available.
There are two timers: the delay timer and the sound timer. Both
timers count down about 60 times per second when nonzero; the
speaker will beep whenever the sound timer is nonzero.
In the instruction table below, NNN is a 12-bit address, KK is an
8-bit constant, and X and Y are 4-bit register numbers. Hex
characters represent themselves. The two first characters of the
instruction code form the lower-address byte of the instruction,
the first character being the more significant nibble.
Instructions marked with (*) are new in SUPER-CHIP.
00CN* Scroll display N lines down
00E0 Clear display
00EE Return from subroutine
00FB* Scroll display 4 pixels right
00FC* Scroll display 4 pixels left
00FD* Exit CHIP interpreter
00FE* Disable extended screen mode
00FF* Enable extended screen mode for full-screen graphics
1NNN Jump to NNN
2NNN Call subroutine at NNN
3XKK Skip next instruction if VX == KK
4XKK Skip next instruction if VX <> KK
5XY0 Skip next instruction if VX == VY
6XKK VX := KK
7XKK VX := VX + KK
8XY0 VX := VY, VF may change
8XY1 VX := VX or VY, VF may change
8XY2 VX := VX and VY, VF may change
8XY3 VX := VX xor VY, VF may change
8XY4 VX := VX + VY, VF := carry
8XY5 VX := VX - VY, VF := not borrow
8XY6 VX := VX shr 1, VF := carry
8XY7 VX := VY - VX, VF := not borrow
8XYE VX := VX shl 1, VF := carry
9XY0 Skip next instruction if VX <> VY
ANNN I := NNN
BNNN Jump to NNN+V0
CXKK VX := pseudorandom_number and KK
DXYN* Show N-byte sprite from M(I) at coords (VX,VY), VF :=
collision. If N=0 and extended mode, show 16x16 sprite.
EX9E Skip next instruction if key VX pressed
EXA1 Skip next instruction if key VX not pressed
FX07 VX := delay_timer
FX0A wait for keypress, store hex value of key in VX
FX15 delay_timer := VX
FX18 sound_timer := VX
FX1E I := I + VX
FX29 Point I to 5-byte font sprite for hex character VX
FX30* Point I to 10-byte font sprite for digit VX (0..9)
FX33 Store BCD representation of VX in M(I)..M(I+2)
FX55 Store V0..VX in memory starting at M(I)
FX65 Read V0..VX from memory starting at M(I)
FX75* Store V0..VX in RPL user flags (X <= 7)
FX85* Read V0..VX from RPL user flags (X <= 7)
Notes on the HP48SX implementation
----------------------------------
CHIP-8 programs are stored in the HP48SX as string objects con-
taining the bytes of the program in increasing address order,
beginning with the byte at 0200. The interpreter itself is a
machine code object that should be run with the CHIP-8 program
string on level 1. 4 kB of free memory is needed. If an error is
detected during execution, the address of the current CHIP-8
instruction is returned as a binary integer on level 1.
To quit, press the backspace key. Pressing ENTER restarts the
CHIP-8 program, and the +/- key turns the sound off or on.
Subroutine nesting is limited to 16 levels.
Most chip-8 programs are written for a 16-key hex keyboard with
following layout:
1 2 3 C 7 8 9 /
4 5 6 D This keyboard is emulated on the HP48SX 4 5 6 *
7 8 9 E using the following keys: 1 2 3 -
A 0 B F 0 . _ +
This may cause some confusion with programs requiring numerical
input.
Copyrights, etc
---------------
Parts of this document is copied from the original CHIP-48 docu-
mentation written by Andreas Gustafsson. Below is the original
copyright message for CHIP-48 v2.25
(c) Copyright 1990 Andreas Gustafsson
Noncommercial distribution allowed, provided that this copyright
message is preserved, and any modified versions are clearly marked
as such.
The program makes use of undocumented low-level features of the
HP48SX calculator, and may or may not cause loss of data, ex-
cessive battery drainage, and/or damage to the calculator hard-
ware. The author takes no responsibility whatsoever for any damage
caused by the use of this program.
THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESSED OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PUR-
POSE.
The modifications from CHIP v2.25 to S-CHIP v1.1 is made by
Erik Bryntse
(erikmb@etek.chalmers.se)
Download file in ASC-format
---------------------------
Download to your 48, use ASC-> and store as SCHIP.
To run a game, press SCHIP with the game string in level 1.
%%HP: T(3)A(R)F(.);
"CCD20EE0108FB97608FFBA81346C1208FD7B5013281AF04346C100CA81AF0281
AF1C134AF2154716F154716F370000100415C781AF143417000C213434B55078
0821837D51341550780821807B418F2D76081AF123400400C213414713514334
C2A208A6A1174143818F843400C108B23134FFFFF81AF0B6E3617471218F2D76
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1AF0B81AF143482000C2134D2144163144345C100C2134D215407BA2D2328311
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3408F000EF21118A64003D23108EA3408F000EF681AF017CC014E96A80A6E14C
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136818F0D8BA40DA0177EEDAD2310E8A6141143417000CA3104D5130146134AF
2154716F154716F14C818F04A6D96D7D0331EE8A68311434C2000C21341428A8
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17015571C01510A6F50D03D6F68180AB90A606F80D1A888A90011434CA100CA1
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134184A6F59CAF08A912146184135151717F1517818F948AD3E03027BBB55280
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0013615A113617114F1C10E6214C03610281AF14345C100C2134156090A60619
071F848D90A6F74D381AF1877F91087A3AD731F10E6631F30E63171AE215F0A6
2AE53102B61550AE1AE215F0B6980D080CF2EA82201C17AD475A38EAB9FAE22E
90A50B6614C20037253118C6112C210878B9D731F30E6631F70E63171AF2AF11
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216414210316401D6C4C4C2114CA3417000C2135DB819F2819F210A31300E633
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08186019E650AE6A6E80D01561A9A0E1791A50B65A9F0E1AB9F0E17154120A4E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"akcs.falco@hpcvbbs.UUCP (Andrey Dolgachev) (05/29/91)
Regarding Super-Chip 1.1, has anyone got the ASC string to compile? I've
never had any problems with d/l and ASC->'ing, so I think there is
something wrong with the string, like the first time Erik posted S-CHIP.
I'll post this reply (obviously) and I'll mail a message to Erik, just in
case.
---Falcodohm@magnus.acs.ohio-state.edu (Peter J Dohm) (05/29/91)
There is one extra space on the end of every one of the lines of test. remove them carefully, and it'll work just fine.... You see, i've got freemacs on my pc, that shows spaces if i choose. I never thought it would come in handy until now... :) Pete Dohm _____________________________________________________________________________ | Peter J. Dohm - Comp. Science Major |Consultant On: Magnus | www | | Unix, VMS, MS-DOS Consultant |Operator/Consultant On: KCGL | |. .| | | The Ohio State University |dohm@kcgl1.eng.ohio-state.edu| | ^ | | | dohm@magnus.acs.ohio-state.edu |ak541@cleveland.freenet.edu | | o | | | pete.dohm@osu.edu or dohm.1@osu.edu |dohm@cis.ohio-state.edu | \_/ | -----------------------------------------------------------------------------
jefft@panix.uucp (Jeff Tarr) (06/09/91)
In <6230011@hplred.HP.COM> tibbs@hplred.HP.COM (Kevin W. Tibbs) writes: >>There is one extra space on the end of every one of the lines of test. >>remove them carefully, and it'll work just fine.... >>Pete Dohm >I attempted to use asc-> on the downloaded code only to get an "Invalid >String" error. Seeing your note, I went back to my Mac and attempted to >find ANY extra spaces ANYWHERE - there weren't any. So whatami doin' >wrong?? The problem is that the version you downloaded to your Mac contains linefeeds as well as carriage returns. Although I thought Translate code #3 in the 48sx took care of LF/CRs, it appears to have problems. The easiest method to fix the problem is to strip the LFs from the file. I use Microsoft word. Just open the file, strip the headers/footers (as usual), then select-all. Change the font to 10-point courier. You should see small squares in the leftmost column. Using Option-Mouse select all the boxes. Next hit delete and all the boxes are gone. Save the new file and then transfer it. >Thanks > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >| | "The powers not delegated to the United States by | >| Kevin W. Tibbs | the Constitution, nor prohibited by it to the | >| | States, are reserved to the States respectively, or | >| Email: | the people." | >| tibbs@hplred.HP.COM | - Tenth Amendment to The Constitution | >| | | > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- ---- Jeff Tarr, Jr.