refactored LOAD routine so that it's parts are reuseable

c64/aliases/,aliases_ram_lowmem.s

@@ -1,33 +1,92 @@
 ;;
-;; Names of ZP and low memory locations (only the implemented ones)
+;; Names of ZP and low memory locations
 ;; (https://www.c64-wiki.com/wiki/Zeropage)
 ;;
 
-	;; $000-$001 - 6502 CPU registers
+	;; $00-$01 - 6502 CPU registers are here
 
+    ;;
+	;; Page 0 - BASIC area ($02-$8F)
+    ;;
+	
+	.alias TXTTAB     $2B
+
+    ;;
+	;; Page 0 - Kernal area ($90-$FF)
+    ;;
+	
+	.alias IOSTATUS   $90
+	.alias STKEY      $91 ; Keys down clears bits. STOP - bit 7, C= - bit 6, SPACE - bit 4, CTRL - bit 2
+	
+	.alias VERCK      $93 ; 0 = LOAD, 1 = VERIVY
+	
+	.alias C3PO       $94 ; flag - is BSOUR content valid
+	.alias BSOUR      $95 ; serial bus buffered output byte
+
+	.alias LDTND      $98 ; number of entries in LAT / FAT / SAT tables
+	.alias DFLTN      $99
+	.alias DFLTO      $9A
+	
+	.alias MSGFLG     $9D ; bit 6 = error messages, bit 7 = control message
+
+	.alias TIME       $A0 ; $A0-$A2, jiffy clock
+
+	;; 2-byte location below seems to be a good place for temporary storage,
+	;; it seems used for timing during tape reads only - see:
+	;; - 'C64 Programmer's Reference Guide', page 314
+	;; - 'Compute's Mapping the Commodore 64', page 32
+	.alias CMP0       $B0 ; $B0-$B1
+	
+	.alias FNLEN      $B7 ; current file name length
+	
+	.alias STAL       $C1 ; $C1-$C2 LOAD/SAVE start address
+
+    ;;
+	;; Other low memory addresses
+    ;;
+	
+	;; Kernal tables for opened files, 10 entries each
+	.alias LAT        $259 ; logical file numbers
+	.alias FAT        $263 ; device numbers
+	.alias SAT        $26D ; secondary addresses
+
+	.alias MEMSTR     $281
+	.alias MEMSIZ     $283 ; NOTE: Mapping the 64 erroniously has the hex as $282, while the DEC is correct
+
+	.alias HIBASE     $288 ; high byte of start of screen
+
+	.alias RSSTAT     $297 ; RS-232 status
+
+	.alias PALNTSC    $2A6 ; 0 = NTSC, 1 = PAL
+	
+	
 	;; Registers for SYS call
-	.alias sys_reg_a $30c
-	.alias sys_reg_x $30d
-	.alias sys_reg_y $30e
-	.alias sys_reg_p $30f
-	.alias sys_jmp   $310
+	.alias SAREG      $30C
+	.alias SXREG      $30D
+	.alias SYREG      $30E
+	.alias SPREG      $30F
 
+	.alias USRPOK     $310 ; JMP instruction
+	.alias USRADD     $311 ; $311 - $312
+	
 	;; Kernal vectors - interrupts
-	.alias CINV      $0314
-	.alias CBINV     $0316 
-	.alias NMINV     $0318
+	.alias CINV       $314
+	.alias CBINV      $316 
+	.alias NMINV      $318
 	
 	;; Kernal vectors - routines
-	.alias IOPEN     $031A
-	.alias ICLOSE    $031C
-	.alias ICHKIN    $031E
-	.alias ICKOUT    $0320
-	.alias ICLRCH    $0322
-	.alias IBASIN    $0324
-	.alias IBASOUT   $0326
-	.alias ISTOP     $0328
-	.alias IGETIN    $032A
-	.alias ICLALL    $032C
-	.alias USRCMD    $032E
-	.alias ILOAD     $0330
-	.alias ISAVE     $0331
+	.alias IOPEN      $31A
+	.alias ICLOSE     $31C
+	.alias ICHKIN     $31E
+	.alias ICKOUT     $320
+	.alias ICLRCH     $322
+	.alias IBASIN     $324
+	.alias IBASOUT    $326
+	.alias ISTOP      $328
+	.alias IGETIN     $32A
+	.alias ICLALL     $32C
+	.alias USRCMD     $32E
+	.alias ILOAD      $330
+	.alias ISAVE      $331
+
+	.alias TBUFFR     $33C ; $33C-$3FB, tape buffer