apps/zasm/instr.asm

@@ -559,14 +559,16 @@ handleLDrr:
 handleRST:
 	ld	a, (INS_CURARG1+1)
 	; verify that A is either 0x08, 0x10, 0x18, 0x20, 0x28, 0x30 or 0x38.
-	; Good news: the relevant bits (bits 5:3) are already in place. We only
-	; have to verify that they're surrounded by zeroes.
-	ld	c, 0b11000111
-	and	c
-	jr	nz, .error
-	; We're in range. good.
-	ld	a, (INS_CURARG1+1)
-	or	c
+	; Good news: they're all multiples of 8.
+	; to verify that we're within range, we to 8-bit rotation. If any of
+	; the first 3 bytes are set (thus not a multiple of 8), the cp 8
+	; later will yield NC because those bits will now be upwards.
+	rrca \ rrca \ rrca
+	cp	8
+	jr	nc, .error
+	; good, we have a proper arg. Now let's get those 3 bits in position
+	rlca \ rlca \ rlca
+	or	0b11000111
 	ld	(INS_UPCODE), a
 	ld	c, 1
 	ret

recipes/ti84/README.md

@@ -1,27 +1,12 @@
 # TI-84+
 
-The TI-84+ is a machine with many advantages, one being that it's very popular.
-It also has a lot of flash memory and RAM.
-
-Its builtin keyboard and screen, however, are hard to use, especially the
-screen. With a tiny font, the best we can get is a 24x10 console.
-
-There is, however, a built-in USB controller that might prove very handy.
+**This is a work-in-progress**
 
 ## Recipe
 
 This recipe gets the Collapse OS shell to run on the TI-84+, using its LCD
 screen as output and its builtin keyboard as input.
 
-## Gathering parts
-
-* [zasm][zasm]
-* A TI-84+ (TI-83+ compatibility is being worked on. See issue #41)
-* A USB cable
-* [tilp][tilp]
-* [mktiupgrade][mktiupgrade]
-* Optional: [z80e][z80e] to emulate
-
 ## Build the ROM
 
 Running `make` will result in `os.rom` being created.
@@ -89,7 +74,6 @@ a "normal" key. The presses must be sequential.
 Keys that aren't a digit, a letter, a symbol that is part of 7-bit ASCII or one
 of the two mode key have no effect.
 
-[zasm]: ../../tools/emul
 [knightos]: https://knightos.org/
 [z80e]: https://github.com/KnightOS/z80e
 [mktiupgrade]: https://github.com/KnightOS/mktiupgrade